CHAPTER 139 BLOOD PROCUREMENT AND SCREENING
CHAPTER 139 BLOOD PROCUREMENT AND SCREENING
An Overview of the Blood Banking System
The System in the United States
Recruitment of Blood Donors
Whole-Blood Donor Screening
Physical and Laboratory Examination of the Blood Donor
Collection of Whole Blood
Preparation of the Venipuncture Site
Venipuncture and Blood Collection
Postdonation Observation and Adverse Reactions to Blood Donation
Special Blood Donations
Autologous Donor Blood
Directed Donor Blood
Collection and Production of Blood Components by Apheresis
Selection of Apheresis Donors
Reactions in Apheresis Donors
Laboratory Testing of Donated Blood
Safety of the Blood Supply
Blood procurement is a vital national priority that is met in the United States by volunteer donors and a pluralistic blood collection program that includes the American Red Cross, independent community blood centers, and hospitals. Over 13 million units of whole blood are collected from about 10 million donors annually. Recruitment of donors is preceded by a medical history and limited physical examination. The donated blood is subjected to as many as 15 tests that include determination of blood type, examination for red cell antibodies, and a series of studies for infectious agents that may be transmitted by blood exchange. The process usually starts with donations from random, unrelated donors but may include autologous, patient-specific, or patient-directed donors in special circumstances. In some cases, collection of platelets, leukocytes, or plasma is achieved by hemapheresis. Plasma for the subsequent manufacture of derivatives such as albumin and intravenous immunoglobulin is obtained from paid donors by for profit organizations different from those that collect whole blood and prepare blood components.
The meticulous attention to donor risk characteristics and the use of sensitive assays to detect infectious agents that may be transmitted by blood has greatly improved the safety of blood as a therapeutic product in countries that apply these practices. Nevertheless, a risk of viral infection, albeit small, remains as new improved methods are developed to move that risk from about one in thirty four thousand to a more remote possibility. The introduction of nucleic acid amplification techniques to detect microbial contaminants should further decrease the risk of acquiring an infection through transfusion.
Acronyms and abbreviations that appear in this chapter include: G-CSF, granulocyte colony stimulating factor; FDA, Food and Drug Administration.
AN OVERVIEW OF THE BLOOD BANKING SYSTEM
THE SYSTEM IN THE UNITED STATES
The United States has a pluralistic rather than a single national system of blood collection.1,2 In the United States during 1994, approximately 13,340,000 units of blood donated by about 10,000,000 people were available for use (Table 139-1). About 92 percent of the blood was collected in 147 regional blood centers, hospitals collected 8 percent, and less than 1 percent was imported from Western Europe.3 Approximately 7.6 percent of the units donated in the United States were autologous donations, and another 2.5 percent were directed donations—that is, blood given by family or friends for a specific patient. A single organization, the American Red Cross, collected about 45 percent of the blood through its network of about 40 regional blood centers. Community blood centers and hospitals collect the remainder. Community blood centers are individual, locally operated, nonprofit organizations, whereas the American Red Cross is a national corporation with a single FDA license and set of operating procedures for all its regional centers.
TABLE 139-1 THE U.S. BLOOD SUPPLY SYSTEM IN 1994*
All whole blood for transfusion in the United States is donated by volunteers; however, costs are incurred in the collection, testing, production, and distribution of blood components. Blood banks are nonprofit organizations that pass on these costs to hospitals. In the past, it was sometimes possible for patients to partially reduce the cost of blood by arranging for replacement of the blood they used. This practice has generally been discontinued because of the demand it places on the patient or family during the difficult time of the illness. Instead, blood banks assume the responsibility of ensuring that the community’s blood needs are met by developing public education and donor recruitment programs.
Some areas of the United States are able to provide more blood than is needed locally, and other areas are unable to collect enough blood to meet their local needs. The misalignment of blood use and blood availability is a long-standing phenomenon. Several inventory-sharing systems are used to move blood around the United States in order to alleviate the shortages, but these are complex and fragile arrangements that are not always effective. As a result, blood shortages occasionally occur in some areas of the United States.
Blood is considered a drug, and all aspects of the selection of donors, collection, processing, testing, preservation, and dispensing are regulated by the FDA as specified in the Code of Federal Regulations. The requirements in the code define the procedures, records, staff proficiency, specific testing, and donor medical requirements that blood banks must follow. Additional standard requirements are formulated by the American Association of Blood Banks, a voluntary organization that accredits blood banks. During the past decade the FDA has required that blood banks implement good manufacturing practices similar to those used by pharmaceutical manufacturers. This has had a major impact on the manner in which blood banks function.1,2,4
There is a considerable difference in the availability of blood and blood components throughout the world.5,6 and 7 In general, this is related to the extent of development in the country and its health care system. For instance, in Third World countries “transfusion practice is fragmented and disorganized and it is difficult, if not impossible, to provide the five basic blood components … in an adequate supply.”8 These countries usually do not have an organized blood supply system, and there may be no system of obtaining a blood supply for the general community. Patients may be required to arrange for the blood they need, and thus, donors may be friends or family members of patients or even individuals who have been paid by the patient’s family to donate the blood needed. There is considerable evidence that blood from paid donors is more likely to transmit disease.9 Donor screening may not be as extensive, transmissible disease testing may be lacking, equipment may be reused, and the blood collected into containers may be unsuitable for the preparation of components. These difficulties may be compounded by the presence of endemic transfusion-transmissible diseases for which screening is difficult or expensive and thus not carried out as extensively as in more developed countries.
It was estimated that in the early 1980s about 75 million units of blood were collected worldwide, about one-third by Red Cross/Red Crescent blood programs.10 In developed countries, especially western Europe and parts of Asia, there is usually a government agency that oversees the blood collection activities, although the extent to which the government sets requirements and monitors or inspects the blood collection system varies.11 Where national blood programs have been developed, usually a national blood policy is established that includes definition of the organization(s) responsible for the program, the source of funding, the type of blood donation, and regulations ensuring blood safety.5,6 In these countries the basic processes of donor medical screening, blood collection, laboratory testing, and preparation of blood components are similar to the U.S. system. In virtually all developed countries blood is donated by volunteers and not paid donors.12 The blood may be collected by hospitals or community-based regional blood centers or some combination of these. The supply systems and sharing among hospitals and blood centers vary with the extent of development of the country’s blood supply system. The basic blood components—red cells, platelets, plasma, and cryoprecipitate—are usually available, and apheresis instruments are used to collect some platelets. Plasma derivatives such as albumin, coagulation factor VIII, and immune globulins are available. In many countries these plasma derivatives are prepared from plasma collected from volunteer donors instead of the paid-donor plasma used to prepare these derivatives in the United States. Thus, the availability of blood and its components around the world varies widely, from inadequate supplies and uncertain safety to sophisticated supply systems and component availability equal to or surpassing those of the United States.
The plasma industry is separate from the blood banking system described above. Plasma can be subjected to a fractionation process to produce several medically valuable products referred to as plasma “derivatives”, such as albumin, fibrinogen, anti-hemophilic factor, and 19 others (see Chap. 143). Plasma fractionation is done in a manufacturing plant setting, in batches of up to 10,000 liters involving the pooling of plasma from as many as 50,000 donors. Plasma for manufacture or fractionation into derivatives can be obtained from units of whole blood, but this amount of plasma is not adequate to meet the needs for plasma derivatives. Therefore, large amounts of plasma are obtained by plasmapheresis. Because only the plasma and not red cells or platelets are removed during the plasmapheresis, individuals can donate plasma up to twice a week. Because of this more extensive commitment to donation, plasma donors are paid and this plasma collection system is usually operated by for-profit organizations and functions separately from the system described above for whole blood donation.
Approximately 11.5 million liters of plasma is collected annually in the United States,13 although exact figures are not known because most plasma is collected by for-profit organizations. There are 22 plasma derivatives approved for licensure by the FDA (see Chap. 143). Some derivatives are produced by only one manufacturer and others by up to six different manufacturers. Thus, disruption in the sources of plasma or in one manufacturer’s plant can have serious consequences and create shortages of certain derivatives.
The remainder of this chapter will describe the blood collection system operated by voluntary community organizations to provide cellular and whole blood–derived components.
RECRUITMENT OF BLOOD DONORS
Although most Americans will require a blood transfusion at some time in their lives, less than 5 percent of the total population, or less than 10 percent of those eligible to donate, have ever done so.13 Most donors give once or infrequently, and thus, much of the nation’s blood supply comes from a small number of dedicated frequent donors.13 Blood donors are more likely than the general population to be male, age 30 to 50, Caucasian, employed, and have more education and higher income.13 There have been some studies of the social psychology and motivation of blood donors,14 but the process is not well understood. It is generally believed that the most effective way to get someone to donate blood is to ask them personally. Factors such as the convenience of donation, peer pressure, receipt of blood by a family member, and perceived community needs are important factors that are superimposed onto the individual’s basic social commitments. Usually blood donors are asked to give to the general community supply. Some donors are asked to give for a specific patient, and this is referred to as directed donation. Such donations may be easier to obtain and leave the donor with a stronger sense of satisfaction because of the personal nature of the donation.13
The heightened concerns about blood safety during the past decade have resulted in expanded requirements for the suitability for blood donation. Thus, a larger proportion of the population of potential donors is being excluded. This, along with the aging population, geographic and ethnic shifts in the population, and people’s changing priorities, are causing a shrinking donor pool. Thus, it will be increasingly important to understand the motivation of blood donors and psychosocial factors that lead to blood donation.
WHOLE-BLOOD DONOR SCREENING
The approach to the selection of blood donors is designed around two themes: to insure the safety of the donor and to obtain a high-quality blood component that is as safe as possible for the recipient. Some specific steps that are taken to insure that blood is as safe as possible are the use of only volunteer blood donors, questioning of donors about their general health before their donation is scheduled, obtaining a medical history before donation, conducting a physical examination before donation, laboratory testing of donated blood, checking the donor’s identity against a donor deferral registry, and providing a method by which the donor can confidentially designate the unit as unsuitable for transfusion after the donation is completed.13
The questions designed to protect the safety of the donor include whether the donor is under the care of a physician and has a history of cardiovascular or lung disease, seizures, present or recent pregnancy, recent donation of blood or plasma, recent major illness or surgery, unexplained weight loss, or unusual bleeding. Medications and age are also documented. Questions designed to protect the safety of the recipient include those related to the donor’s general health, the presence of a bleeding disorder, a history of receipt of growth hormone, and the occurrence of or exposure to patients with hepatitis or other liver disease, AIDS (or symptoms of AIDS), Chagas disease, or babesiosis. A history is also obtained regarding the injection of drugs, receipt of coagulation factor concentrates, blood transfusion, a tattoo, acupuncture, ear piercing, an organ or tissue transplant, travel to areas endemic for malaria, recent immunizations, contact with persons with hepatitis or other transmissible diseases, ingestion of medications (especially aspirin), presence of a major illness or surgery, or previous notice of a positive test for a transmissible disease. In addition, there are several questions related to AIDS risk behavior. These include whether the potential donor has had sex with anyone with AIDS, given or received money or drugs for sex, (for males) had sex with another male, or (for females) had sex with a male who has had sex with another male. This series of sex-related questions is very specific and has changed the interaction and relationship between the donor and the blood bank.
Commonly, situations arise in which the donor’s physician believes that donation would be safe but the blood bank does not accept the donor. For instance, donors with a history of cancer, other than minor skin cancer or carcinoma in situ of the cervix, are usually rejected because the genesis of malignant disease is not known. The donor is questioned about medications. Some medications may make the donor unsuitable because of the condition requiring the medication, while others may be potentially harmful to the recipient. Many other conditions must be evaluated individually by the blood bank physician, and that physician’s assessment of conformance with FDA regulations, which view blood as a pharmaceutical, may not always coincide with the personal physician’s view of the health of the patient who is the potential blood donor.
PHYSICAL AND LABORATORY EXAMINATION OF THE BLOOD DONOR
The examination includes determination of the temperature, pulse, blood pressure, weight, and blood hemoglobin concentration. The FDA has mandated limits for each of these. In addition, the donor’s general appearance is assessed for any signs of illness or the influence of drugs or alcohol. The skin at the venipuncture site is examined for signs of intravenous drug abuse, lesions suggestive of Kaposi sarcoma, and local lesions that might make it difficult to sterilize the skin and thus lead to contamination of the blood unit during venipuncture.
COLLECTION OF WHOLE BLOOD
Blood must be collected into single-use, sterile, FDA-licensed containers. The containers are made of plasticized material that is biocompatible with blood cells and allows diffusion of gases in order to provide optimal cell preservation (see Chap. 140 and Chap. 142). These blood containers are combinations of bags that allow separation of the whole blood into its components in a closed system, thus minimizing the chance of bacterial contamination while making storage of the components for days or weeks possible.
PREPARATION OF THE VENIPUNCTURE SITE
The blood should be drawn from an area free of skin lesions, and the phlebotomy site should be properly sterilized. The site is scrubbed with a soap solution, followed by the application of tincture of iodine or iodophor complex solution. The selection of the venipuncture site and its sterilization are very important steps, since bacterial contamination of blood can be a serious or even fatal complication of transfusion.15,16
VENIPUNCTURE AND BLOOD COLLECTION
The venipuncture is done with a needle that should be used only once in order to avoid contamination. The blood must flow freely and be mixed with anticoagulant frequently as it fills the container, in order to avoid the development of small clots. The actual time for collection of 450 ml is usually about 7 min and almost always less than 10 min. During blood donation there is a slight fall in cardiac output but little change in heart rate. A slight decrease in systolic pressure results, with a rise in peripheral resistance and diastolic blood pressure.17
Usually 450 ml (±10%) is collected, although some blood banks now collect 500 ml from larger donors. This is mixed with 63 to 70 ml of anticoagulant composed of citrate, phosphate, and dextrose (CPD). The amount of blood withdrawn must be within prescribed limits in order to maintain the proper ratio with the anticoagulant; otherwise the blood cells may be damaged and/or anticoagulation may not be satisfactory (see Chap. 140). Although the red cells could be stored in the CPD-anticoagulant solution, it is customary to remove almost all the anticoagulated plasma and resuspend the red cells in a solution that provides optimum red cell preservation (see Chap. 140).
POSTDONATION OBSERVATION AND ADVERSE REACTIONS TO BLOOD DONATION
A reaction occurs following approximately 4 percent of blood donations, but fortunately most reactions are not serious.18,19 Donors who have reactions are more likely to be younger, unmarried, have a higher predonation heart rate and lower diastolic blood pressure, and to be first time or infrequent donors.20 The most common reaction to blood donation involves weakness, cool skin, and diaphoresis. A more extensive but still moderate reaction involves dizziness, pallor, hypertension, and bradycardia. Bradycardia is usually taken as a sign of a vasovagal reaction rather than hypotensive or cardiovascular shock, where tachycardia would be expected. In a more severe form, this kind of reaction may progress to loss of consciousness, convulsions, and involuntary passage of urine or stool. These symptoms also are thought to be due to vasovagal reactions rather than hypovolemia.18 Other reactions include nausea and vomiting; hyperventilation, sometimes leading to twitching or muscle spasms; hematoma at the venipuncture site; convulsions; or serious cardiac difficulties. Such serious reactions are very rare.18,19,21 Injury of the brachial nerve and resulting pain and/or paresthesia may occur due to needle puncture of the nerve or compression from a hematoma.22,23
Donors are advised to drink extra fluids to replace lost blood volume and to avoid strenuous exercise for the remainder of the day of donation. This latter advice is given to avoid fainting and also to minimize the possibility that a hematoma will develop at the venipuncture site. Some donors are subject to lightheadedness or even fainting if they change position quickly. Therefore, donors are also advised not to return to work for the remainder of the day in an occupation where fainting would be hazardous to themselves or others.
SPECIAL BLOOD DONATIONS
There are several situations involving blood donation in which the blood is not being obtained for the community’s general blood supply. Examples of these include autologous donation, directed donation, patient-specific donation, and therapeutic bleeding. In some of these situations the FDA requirements for blood donation may not apply.
AUTOLOGOUS DONOR BLOOD
Autologous blood donation is an old concept but was little used until the AIDS epidemic raised fears of blood transfusion both among patients and physicians. Individuals may donate blood for their own use if the need for blood can be anticipated and a donation plan developed. Most commonly this occurs with elective surgery.
Autologous blood for transfusion can be obtained by preoperative donation, acute normovolemic hemodilution, intraoperative salvage, and postoperative salvage (see also Chap. 140), but only preoperative donation will be discussed here. If patient candidates for autologous blood donation meet the usual FDA criteria for blood donation, their blood may be “crossed over,” that is, used for other patients if the original autologous donor has no need for the blood. This practice is no longer allowed by AABB standards. If the autologous donor does not meet the FDA criteria for blood donation, the blood must be specially labeled, segregated during storage, and discarded if not used by that specific patient. Thus, it is important that the autologous blood donation be collected only for procedures in which there is substantial likelihood that it will be used.24 Without this type of planning, there is a very high rate of wastage of autologous blood, estimated at 52.4 percent in 1994.3 Thus, the cost of autologous blood is quite high.25
There are no age or weight restrictions for autologous donation.13 Pregnant women may donate, but this is not recommended routinely since these patients rarely require transfusion. The autologous donor’s hemoglobin may be lower (11 g/dl) than that required for routine donors (12.5 g/dl), and autologous donors may donate as often as every 72 h up to 72 h prior to the planned surgery, although usually it is only possible to obtain two to four units of blood before the hemoglobin falls below 11 g/dl. Autologous blood donors can be given erythropoietin and iron in order to increase the number of units of blood they can donate,26 although the value of erythropoietin remains a bit unclear since this strategy has not been shown to reduce the need for allogeneic donor blood.27 Some contraindications for autologous blood donation are bacteremia, symptomatic angina, recent seizures, and symptomatic valvular heart lesions. However, the final decision whether to withdraw blood from an autologous donor rests with the medical director of the blood bank. Often consultation between the donor’s (patient’s) physician and the blood bank physician is necessary in order to decide on a wise course of action.
Autologous blood must be typed for ABO and Rh antigens, and at least the first unit must be tested for transmissible diseases.13 If any of the transmissible disease tests are positive, the unit must be labeled with a biohazard label. This is sometimes confusing or disconcerting to physicians, but it is an FDA requirement, intended to alert health care personnel to the potential hazard presented by the potentially infectious blood.
DIRECTED DONOR BLOOD
Directed donors are friends or relatives who wish to give blood for a specific patient because the patient hopes those donors will be safer than the regular blood supply. In general, the data do not indicate that directed donors have a lower incidence of transmissible disease markers,28,29 and thus there may not be a realistic rationale for these donations. When friends or relatives are asked to donate blood, they may be reluctant to disclose risk factors that would preclude them from voluntary donation. Some blood banks refuse such donations, but most accept them as a service to the patients. However, because their blood becomes part of the community’s general blood supply if it is not used for the originally intended patient, directed donors must meet all the usual FDA requirements for routine blood donation.
There are a few situations in which appropriate transfusion therapy involves collecting blood from a particular donor for a particular patient. Examples are donor-specific transfusions prior to kidney transplantation, maternal platelets for a fetus projected to have alloimmune neonatal thrombocytopenia, or family members of a patient with a rare blood type. In these situations donors must meet all the usual FDA requirements, except that they may donate as often as every 3 days so long as the hemoglobin remains above the normal donor minimum of 12.5 g/dl.13 These units must undergo all routine laboratory testing.13
Blood may be collected as part of the therapy of diseases such as polycythemia vera or hemochromatosis. Often the patient or the physician asks that the blood be used for transfusion as a way of comforting the patient. However, usually such blood is not used for transfusion since such donors do not meet the FDA standards for donor health.
COLLECTION AND PRODUCTION OF BLOOD COMPONENTS BY APHERESIS
Blood components can be obtained by apheresis rather than being prepared from a standard unit of whole blood. In apheresis the donor’s anticoagulated whole blood is passed through an instrument in which the blood is separated into red cells, plasma, and a leukocyte/platelet fraction (see Chap. 144). Several semiautomated blood cell separator instruments are available for the collection of platelets, granulocytes, peripheral blood stem cells, mononuclear cells, or plasma.13 All of these instruments use centrifugation to separate the blood components.30 Some apheresis procedures involve two venipunctures with continuous flow of blood from the donor through the blood cell separator and others can be accomplished with a single venipuncture and intermittent blood withdrawal and return.
In the past most platelet concentrates have been produced from whole blood, but plateletpheresis has been used increasingly, so that by 1992, 46 percent of platelets produced in the United States were produced by plateletpheresis.3 Plateletpheresis requires about 90 min, during which about 4000 to 5000 liters of the donor’s blood is processed through the blood cell separator. This results in a platelet concentrate with a volume of about 200 ml and containing about 3.5 × 1011 platelets and less than 0.5 ml red cells. Recently manufactured blood cell separators produce a platelet concentrate that contains less than 5 × 106 leukocytes and thus can be considered leukocyte depleted. Following plateletpheresis the donor’s platelet count declines by about 30 percent and does not return to pre-plateletpheresis levels for about 4 days31 (see Chap. 142).
Leukapheresis has been used to produce a granulocyte concentrate for transfusion therapy of infections unresponsive to antibiotics.13 In the past, leukapheresis provided only a marginally adequate dose of granulocytes for therapeutic benefit,31 and its use had declined to very low levels (see Chap. 141). Leukapheresis is usually a more lengthy and complex procedure than plateletpheresis. Because the efficiency of granulocyte extraction from whole blood is less than for platelets, the leukapheresis procedure involves processing 6500 to 8000 ml of donor blood during about 3 h.30 To increase the separation of granulocytes from other blood components, hydroxyethyl starch is added to the blood cell separator flow system.30 In addition, glucocorticoids have been administered to the donor to increase the peripheral blood granulocyte count and thus increase the yield.29 Recently, G-CSF has been administered to granulocyte donors to achieve much larger increases in granulocyte count and a much greater granulocyte yield.32,33,34 and 35 Transfusion of these high-yield granulocyte concentrates results in substantial increases in the granulocyte count and has led to a renewed interest in granulocyte transfusions36 (see Chap. 141).
Plasmapheresis can be done using sets of multiple attached bags, but this is time consuming and cumbersome and involves disconnecting the blood bags from the donor, resulting in the chance of returning the blood to the wrong donor. During the past few years semiautomated instruments have become available that require less operator involvement than the bag systems, while producing larger volumes of plasma more rapidly. The volume of plasma that can be collected depends on the size of the donor. Plasmapheresis can usually be done in about 30 min to produce up to 750 ml of plasma, depending upon the size of the donor. Very few red cells are removed. The procedure can be repeated up to twice weekly, so that theoretically a donor could provide up to about 50 liters of plasma in 1 year (see Chap. 144).
SELECTION OF APHERESIS DONORS
The selection of donors for plateletpheresis, leukapheresis, and plasmapheresis uses the same criteria as whole-blood donation.13 Because of the unique nature of apheresis there are some additional donor requirements. Because many apheresis procedures involve two venipunctures and continuous blood flow, good venous access is important. No more than 15 percent of the donor’s blood should be extracorporeal during apheresis, and thus, the donor’s size is considered when making decisions about specific apheresis procedures or instruments to be used. Following plateletpheresis, the donor’s platelet count declines by about 30 percent and does not return to pre-plateletpheresis levels for about 4 days.30 Donors may undergo plateletpheresis every 48 h, although if they are donating more often than every 8 weeks a platelet count must be done to ensure that it is at least 150,000/µl (1.5 × 1011/liter).31 Following leukapheresis of G-CSF-stimulated donors the granulocyte count decreases slightly, the platelet count by 20 to 25 percent, and the hematocrit by about 1 percent.34,35 Thus, the platelet count must be monitored in donors undergoing frequent leukaphereses. Because a plateletpheresis concentrate would be the sole source of platelets for the transfusion, the donor must not have taken aspirin for at least 3 days. For donors undergoing plasmapheresis more often than once every 8 weeks, the serum protein must be at least 6 g/dl, and every 4 months a protein electrophoresis or a quantitative immunoglobulins assay should be obtained and the results must be normal to allow further donation.13 The amount of blood components removed from apheresis donors must be monitored. Not more than 200 ml of red cells per 2 months or approximately 1500 ml of plasma per week may be removed.13 The laboratory testing of donors and apheresis components for transmissible diseases is the same as for whole-blood donation. Thus, the likelihood of disease transmission from apheresis components is the same as from whole blood.
REACTIONS IN APHERESIS DONORS
Apheresis donors can experience the same kind of reactions as whole-blood donors. In addition, apheresis donors experience a higher incidence of paresthesias, probably due to the infusion of the citrate used to anticoagulate the donor’s blood while it is in the cell separator. This type of reaction is managed by slowing the flow rate of the instrument and thus slowing the rate of citrate infusion. The additional donor selection and monitoring requirements for apheresis prevent the development of reactions or complications due to excess removal of blood cells or plasma. In leukapheresis, donors may be given glucocorticoid and/or G-CSF to elevate the granulocyte count, and the sedimenting agent hydroxyethyl starch is used in the cell separator to improve the granulocyte yield. When G-CSF is used about 60 percent of donors experience side effects, usually myalgia, arthralgia, headache, or flulike symptoms.32,33,34 and 35 This rate of side effects may be higher if the donors also receive glucocorticoids.35 The major side effect of hydroxyethyl starch is blood volume expansion manifested by headache and/or hypertension.13 Donor selection techniques are intended to minimize the likelihood of hypertension due to hydroxyethyl starch.
LABORATORY TESTING OF DONATED BLOOD
Each unit of whole blood or each apheresis component undergoes a standard battery of tests (Table 139-2), including those for the blood type, red cell antibodies, and transmissible diseases. Additional tests, such as those for cytomegalovirus or HLA antibodies, may be done optionally. Eight tests, six of which have been introduced since 1985, are performed for transmissible diseases.1 The total number of test results for each unit of donated blood is about 15, depending on the specific methodology used. In addition, since each unit of whole blood is separated into several components and there is a donor history record and two or three tubes of blood for tests, each donation generates up to 30 different data elements. All data are amalgamated in order to ensure that they are satisfactory for release of the blood into the transfusion inventory. Since busy blood collection centers deal with hundreds of donors each day, this virtual explosion of data has made it essential that blood banks operate sophisticated computer systems and, where possible, automated laboratory testing equipment. Thus, the modern blood center uses pharmaceutical-type manufacturing processes in order to ensure accuracy and cost-effectiveness.2,4,13
TABLE 139-2 LABORATORY TESTS OF DONATED BLOOD
SAFETY OF THE BLOOD SUPPLY
Ironically, the improvements in blood safety have occurred at a time of increased fear of transfusion in the public and more caution in the use of blood components by physicians. The steps in donor selection and laboratory testing described above have resulted in the nation’s blood supply being safer than it has ever been.1 Each step in the overall process of donor evaluation and testing adds to blood safety in important ways. For instance, in San Francisco, changes in the medical history and donor selection criteria caused a 90 percent decrease in the HIV infectivity of the blood supply even before the introduction of a test for HIV.37 The introduction of new tests for transmissible diseases has further reduced the proportion of infectious donors. Screening of the donor’s identity against donor deferral registries detects individuals who have been previously deferred as blood donors but who for various reasons attempt to donate again. These and many other changes have resulted in the improvement in blood safety. The risk of acquiring a transfusion-transmitted disease ranges from 1 per 103,300 units for hepatitis C to 1 per 493,000 for HIV (Table 139-3). Thus, although the blood supply is safer than ever, transfusion is not risk-free and should be undertaken only after careful consideration of the patient’s clinical situation and specific blood component needs (see Chap. 140).
TABLE 139-3 TRANSFUSION-TRANSMITTED DISEASES*
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Berry PR, Wallis WE: Venipuncture nerve injuries. Lancet 1:1236, 1997.
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Starkey NM, MacPherson JL, Bolgiano DC, et al: Markers for transfusion-transmitted disease in different groups of blood donors. JAMA 262:3452, 1989.
Williams AE, Kleinman S, Gilcher RO, et al: The prevalence of infectious disease markers in directed versus homologous blood donations (abstract). Transfusion 32:45S, 1992.
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Ernest Beutler, Marshall A. Lichtman, Barry S. Coller, Thomas J. Kipps, and Uri Seligsohn