Articles on Medical Diseases and Conditions

Category: Undesirable Effects of Blood or Blood Product Transfusion

Undesirable Effects of Blood or Blood Product Transfusion

  • Massive Blood Transfusion

    Massive blood transfusion is defined by the AABB as replacement of the patient’s blood volume (equivalent to 8-10 units of whole blood in a 70-kg person) within 12 hours (some define the time period as 24 hours). Transfusion of such volumes presents special difficulties, depending on the substance being transfused and the rate of administration. By the end of a transfusion sufficient to replace the equivalent quantity of one blood volume, roughly one third of any substance originally in the patient’s blood will remain (range 18%-40%), predominantly because of dilution with transfused material. The most common and serious complication of massive transfusion is bleeding; the most common identifiable cause is platelet related, with factor deficiency next most frequent. Massive transfusion is sometimes complicated by disseminated intravascular coagulation (reported in 5%-30% of severely traumatized patients).

    Citrate anticoagulant may cause difficulty when large volumes of whole blood are given in very short periods of time. Citrate has calcium-binding activity that may lead to hypocalcemia and also has a potential depressant effect on the myocardium. Ionized calcium measurement is much more helpful to assess this possibility than total serum calcium. Citrate is metabolized in the liver. Most patients are able to tolerate a large amount of citrate if liver function is adequate. However, some patients have poor liver function. One investigator states that the average person could receive one unit of whole blood every 5 minutes without requiring calcium supplements. At the other extreme, some have used 1 ampule (1 gm) of calcium gluconate for every five units of citrated whole blood. Calcium chloride has four times as much calcium as calcium gluconate, so that dosage using calcium chloride must be reduced proportionately. The majority of investigators currently deemphasize need for calcium supplements, and use of packed RBCs considerably reduces the amount of transfused citrate. Temperature of transfused blood is ordinarily not a problem. However, large amounts of rapidly administered cold blood increase the possibility of ventricular fibrillation. Ordinarily, blood can be allowed to warm in room air; if this is not possible, one can use a water bucket (30°C) for unopened blood containers or special warming devices (37°C) through which the blood passes via tubing while being administered. Transfusion of blood at ordinary speed does not require warming. Coagulation factor deficiency must be considered during massive transfusion. This involves primarily the labile factors V and VIII. Factor V has a storage half-life of about 10-14 days (range, 1-16 days), and levels in stored whole blood may be 30% (of normal) or even less in stored whole blood at 21 days. Factor VIII has a half-life of about 5-10 days (range, 1-16 days), and the level in stored whole blood is reported to be 15%-30% at 21 days. Lesser amounts would be present in packed RBCs due to the decreased amount of plasma. In either case, transfused material would probably contribute some factor V and VIII activity to residual patient activity. Whereas some have advocated transfusing 1 unit of fresh blood (or fresh frozen plasma or cryoprecipitate) for every 5 units or 10 units of stored whole blood during massive transfusion, a 1984 Consensus Development Conference on Fresh-Frozen Plasma stated that there is no evidence that the prophylactic use of fresh frozen plasma is necessary unless documented coagulation defects due to factor V or VIII deficiency are present. Coagulation defects are manifest by abnormal bleeding or oozing (not accounted for by failure to ligate damaged blood vessels). One relatively frequent contributing problem is concurrent disseminated intravascular coagulation due to tissue damage from trauma or tissue hypoxia from blood loss.

    Platelets. Platelets devitalize rapidly on storage if they are not separated from RBCs. In fresh whole blood, platelets are about 60% effective at 24 hours and almost completely ineffective after 48 hours. Ordinary bank blood or packed RBCs, therefore, essentially have no functioning platelets, even though the platelet count may be normal. This may produce difficulty in massive transfusions using stored bank blood or packed RBCs, although there is usually no problem when administration takes place over longer periods of time. After one total blood volume replacement, the majority of patients still have platelet counts of roughly 100,000/mm3 or more due to the 35%-40% of original platelet count remaining plus some mobilization of platelets from the spleen and bone marrow. However, the platelet count may reach 50,000/ cu mm or less with not all of these platelets being functional. Nevertheless, the 1986 Consensus Conference on Platelet Transfusion Therapy noted that most patients undergoing massive transfusion do not bleed because of dilutional thrombocytopenia alone and recommended that evidence of clinically abnormal bleeding or oozing plus thrombocytopenia be present before transfusing platelets rather than prophylactic administration of platelets.

  • Neonatal Transfusions

    Besides many of the problems seen with adult transfusion, in neonates there are additional difficulties related to the small blood volume of the infant, the immaturity of the immune system and some of the enzyme systems, and the relatively high hematocrit level of the newborn. On the positive side, up to age 4 months the infant rarely forms alloantibodies against red cell antigens. It has been reported that the most common need for transfusion is to correct anemia due to blood drawn for laboratory tests. The hematocrit level of transfused blood to correct anemia must be adjusted to approximately 65%. Generally, aliquots of 20-60 ml are prepared from single-donor units. If the donor blood has been stored and contains additives, it may be necessary to wash the RBCs in order to remove some of the additives, especially in premature or seriously ill infants. Although transfusion criteria vary, one published guideline advocates transfusion to maintain the hematocrit level at 40% in newborns or in neonates on ventilators or needing oxygen support. Transfusion also would be considered if more than 10% of the infant’s blood volume were withdrawn for laboratory tests within a 10-day period.

    Exchange transfusion at one time was commonly performed for HDN, but with the use of phototherapy the need for exchange transfusion is uncommon. Some have used exchange transfusion in occasional patients with sepsis or disseminated intravascular coagulation and in premature infants with severe respiratory distress syndrome. If the mother and infant have the same ABO group, group-specific RBCs are used. If the ABO groups are different, group O cells are used. If the infant is Rh positive, Rh positive blood can be used unless an anti-D antibody is present; in this case, Rh negative blood is necessary. The mother’s serum is generally used to crossmatch the donor. Donor blood less than 1 week old in CPDA-1 anticoagulant is most frequently used. It is considered desirable that the blood not have cytomegalovirus antibodies or hemoglobin S. A donor blood hematocrit level of 40%-50% is preferred and can be adjusted in several ways. If the newborn develops polycythemia (hematocrit level of 65% or more during the first week of life), partial exchange transfusion with replacement by crystalloids or 5% albumin would be necessary in order to lower the hematocrit to a safer level of 55%-60%.

    Platelet transfusions may have to be given for bleeding due to thrombocytopenia of DIC, infection, or antiplatelet antibodies. Antiplatelet antibodies may be due to maternal idiopathic thrombocytopenic purpura (ITP) or due to maternal sensitization and antibody production from a fetal platelet antigen that the mother lacks (most commonly P1A1). In these cases, IV immune globulin (IVIG) may be helpful as well as platelet transfusion. However, there are conflicting reports on whether IVIG has a significant beneficial effect.

  • Other Transfusion Problems

    As noted in Chapter 9, concentrated immune gamma globulin (IV-GG) may contain red cell antibodies and also antibodies against various infectious agents such as hepatitis viruses, cytomegalovirus, and Epstein-Barr virus. Enough IV-GG may be transfused so that the transfused antibodies are detectable in recipient serum. This may cause problems in differential diagnosis of infection and significance of red cell antibodies unless the IV-GG therapy is known to the blood bank and all consultants.

    Storage of red blood cells. After approximately two thirds of RBC shelf life, some of the RBCs lose vitality and become spherocytes. Since spherocytosis is a feature of certain isoimmune and autoimmune hemolytic anemias, transfusion of such blood before diagnostic investigation may cause confusion. Potassium concentration slowly rises during storage as it escapes from devitalized RBCs. After about two thirds of RBC shelf life, plasma potassium levels reach about 18 mEq/L, roughly four times normal. Although the hyperkalemia of stored RBCs seems to have little effect on most persons, even when many units are transfused, it may be undesirable if the patient already has an elevated serum potassium level, as seen in uremia or acute renal failure. Ammonium levels of stored blood also increase and may reach values of 10-15 times normal toward the expiration date of the RBCs. Transfusion of large volumes of such blood may be dangerous in patients with severe liver disease. Medications in donor blood theoretically could be a problem to the recipient. This is rarely mentioned in the medical literature, possibly due to current use of packed RBCs rather than whole blood.

  • Infections Transmitted by Transfusion

    Bacterial infection from contaminated blood or blood products is rare as long as continuous adequate refrigeration is provided. Platelets are especially apt to develop bacterial growth when stored at room temperature. The spirochetes of syphilis usually die after refrigerated storage for 4-5 days. Malaria could be transmitted in blood from infected travelers or immigrants from endemic areas. Virus infections are a much greater problem. These infections are discussed in detail in Chapter 17 and will be mentioned only briefly here.

    Hepatitis virus infection. This subject is discussed more completely in Chapter 17. Transfusion-related hepatitis virus infection used to occur in about 10% of transfused patients (range, 0.02-25%) and as high as 50% in those who received many transfusions. However, only about 10% of these infections were symptomatic. An estimated 90% of life-threatening viral infections have been eliminated by pretransfusion donor testing for hepatitis virus B and C, human immunodeficiency virus-1 and 2 (HIV-1 and 2), and human T-cell leukemia virus-I and II (HTLV-I and II). About 5%-10% of transfusion-related hepatitis virus infections are now due to hepatitis B. Mandatory screening of donor blood for hepatitis B surface antigen (HBsAg) and the core antibody (HBcAb), in addition to attempts to eliminate high-risk carrier groups among donors by careful questioning and reliance on nonpaid volunteer donors, has eliminated more than 90% of hepatitis B transfusion-related infections. Use of frozen RBCs was originally thought to eliminate hepatitis B virus infectivity, but this has proven to be untrue, although the incidence of transmission may be somewhat reduced. Therefore, whole blood, packed RBCs, and some blood products can transmit hepatitis virus infection. In general, single-donor products are less likely to carry infection than pooled-donor products. Two percent to 12% of persons who test positive for HBsAg are also carriers of delta hepatitis virus (hepatitis D virus), a virus that requires a liver cell already infected by hepatitis B to replicate. Therefore, a small percentage of patients infected by hepatitis B virus develop superimposed hepatitis D virus. Serologic tests for hepatitis D virus are now available. A very small number of transfusions carry hepatitis A virus.

    It is not currently recommended to give either immune human serum globulin or hepatitis B immune globulin (HBIG) to prevent hepatitus B virus (HBV) or HIV infections. Neither have prevented HBV infection in the virus dose received from transfusion; and the evidence to date regarding hepatitus C virus (HCV) is conflicting. Albumin or immune globulin have not been reported to cause HIV or hepatitis virus infection.

    Currently, about 85%-90% of transfusion-related hepatitis virus infections are due to HCV. The carrier rate for HCV in the volunteer donor population is said to be about 1.5%. Before a serologic test for HCV antibody was available, blood banks tried to eliminate donor blood that might contain HCV by testing donors for alanine aminotransferase (ALT, formerly SGOT), which is usually elevated in active hepatitis virus infection, and for HBV core antibody, which is associated with about a 3-fold increased incidence of HCV in addition to indicating HBV. These two tests were thought to eliminate about one third of donor blood carrying HCV. When HCV antibody tests first became available, sensitivity of the tests was estimated to be about 50% and the tests produced about 50% false positive reactions. The third generation HCV antibody tests available in 1993 appear to have 80% sensitivity and less than 10% false positive results.

    Cytomegalic inclusion virus. After hepatitis virus, the most frequent transfusion-related virus infection is cytomegalovirus (CMV). The carrier rate for CMV in the donor population is reported to be 6%-12%, whereas 35%-70% of donors have antibody to CMV. The percentage of infected persons who develop symptoms is not well documented, but most of those who have symptoms display an illness clinically resembling infectious mononucleosis (“heterophil-negative mononucleosis”). The disease is most serious when contracted by immunocompromised persons, transplant patients, and premature infants of low birth weight. Serologic tests for CMV antibody are now available and are used by some institutions to screen donor blood intended for low birth weight newborns and some immunocompromised persons. Since CMV is carried by WBCs, washed RBCs and frozen RBCs are reported to have a lower incidence of CMV infection than standard packed RBCs. However, best results are obtained with special leukocyte removal filters.

    Human immunodeficiency virus. The third important virus group is the HIV-I, the cause of acquired immunodeficiency syndrome (AIDS) and the various pre-AIDS conditions. Studies have indicated a 65%-70% rate of recipient infection (based on appearance of HIV-I antibody in recipients) from antibody-positive donor blood. Until 1986, about 2% of AIDS was due to transfusion of blood or blood products. Current mandatory donor blood screening tests for HIV-I antibody plus attempts to persuade high-risk persons not to donate are thought to have eliminated well over 95% of infected donor blood. Heat treatment of factor VIII concentrate also reduces the incidence of HIV-I transmission; this plus donor testing has virtually eliminated factor VIII concentrate infectivity by HIV-I. Unfortunately, heat treatment does not affect hepatitis virus infectivity. Therapeutic immune globulin is also free of HIV infectivity due to the way it is prepared, although the preparations may contain detectable antibody against HIV-I. This passively transferred antibody may be responsible for a false positive HIV-I antibody test result, which may persist for as long as 6 months, if the recipient is tested for HIV antibodies. More recently, another member of the HIV family called HIV-2 was discovered in Africa; after it began spreading elsewhere, tests were developed and mandated for blood bank use.

    HTLV-I, which causes human T-cell leukemia, and HTLV-II, which may be associated with hairy cell leukemia (Chapter 7), can also be transmitted by transfusion. Transmission of HTLV-I could be a problem in donor blood from endemic areas, such as Japan and the Caribbean. Tests for HTLV-I and II are also now in use in blood banks. Finally, other viruses, such as the Epstein-Barr virus, can also be transmitted by transfusion.

  • Anaphylactic Reactions

    Immunoglobulin A antigen reactions. Immunoglobulin A (Chapter 22)is the principal immunoglobulin in such human secretions as saliva, bile, and gastric juice. Class-specific anti-IgA occurs in patients who lack IgA; these persons may be clinically normal or may have such disorders as malabsorption syndrome, autoimmune disease, or recurrent sinus or pulmonary infection. Interestingly, only 40% develop anti-A antibodies. Limited specificity anti-IgA occurs in persons who have normal IgA levels but who become sensitized from exposure to human plasma proteins from blood transfusion or pregnancy. Anti-IgA antibodies produce reaction only in transfusions that include human plasma proteins and are considered to be a type of anaphylactic reaction. Symptoms consist of tachycardia, flush, headache, dyspnea, and sometimes chest pain. Typically there is no fever. Severe episodes may include hypotension. Again, these are nonspecific symptoms that could be produced by leukoagglutinins or hemolytic reactions. Tests to prove IgA incompatibility are available only in a few medical centers; therefore, the diagnosis is rarely confirmed. Substantially decreased IgA on serum IgA assay would be presumptive evidence of anti-IgA reaction of the class-specific type. IgA immunologic reactions can be prevented by eliminating donor plasma proteins through the use of washed cells or frozen cells.

  • Tissue-Organ Immunologic Reactions

    Graft-vs.-host disease (GVHD)

    Graft-vs.-host disease (GVHD) results from introduction of sufficient HLA-incompatible and immunologically competent donor lymphocytes into a recipient who is sufficiently immunodeficient that the incompatible donor cells cannot be destroyed. The donor lymphocytes proliferate and attack tissues of the new but incompatible host. There are two clinical types, organ transplants (represented here by bone marrow transplant) and blood transfusion. In bone marrow grafts the donor lymphocytes are in the graft. Current reports indicate that 60%-70% of patients with bone marrow grafts from HLA-compatible siblings (not identical twins) develop some degree of GVHD symptoms, and 10%-20% of marrow transplant patients die from it.

    Graft-vs.-host(GVH) transplant disease can be acute or chronic. In bone marrow transplants, the acute type clinically begins about 10-28 days after transplantation; the first symptom usually is a skin rash. This is a somewhat longer time interval than onset in transfusion-related GVHD. About 20%-50% of HLA-compatible marrow transplant patients develop some degree of acute onset GVHD. Chronic GVHD occurs in 25%-45% of longer-term marrow transplant survivors; it typically appears 100 days or more after transplantation, but it can occur as early as 50 days or as late as 15 months. Persons under age 20 years have a relatively good chance of escaping or coping with GVHD, while those over age 50 have the worst prognosis. Marrow transplant patients develop B-lymphocyte lymphoproliferative disorders (benign, premalignant, or malignant lymphoma) in about 0.6% of cases. This is often associated with evidence of Epstein-Barr viral infection.

    In the other clinical category of patients, transfusion is the usual cause. Patients at risk are those receiving intrauterine or neonatal exchange transfusions, and in congenital immunodeficiency syndromes, malignancy undergoing intensive chemotherapy (especially when combined with radiotherapy), and aplastic anemia. Incidence of posttransfusion graft-vs.-host syndrome in these conditions is not known with certainty but varies from 0%-8%, depending on the disease, therapy, and institution. The highest incidence appears to be in malignant lymphoma. In classic cases the syndrome develops 1-2 weeks (range 3 days-6 weeks) after transfusion and consists of fever, severe diarrhea, pancytopenia, hepatitis, and skin rash. Up to 90% of patients with a transfusion-related full-blown syndrome die, usually from infection. Both transplant and transfusion syndromes can be prevented by gamma radiation treatment of the blood product being transfused, in doses sufficient to affect lymphocytes but not other blood cells (usually 25 Gy = 2,500 rads). The AABB recommends radiation for all donors related by blood to the recipient. The greatest incidence of GVHD from blood-related donors is from first-degree blood relatives. RBC transfusion itself has immunologic effects on the recipient. It has been shown that random-donor blood transfusions before renal transplant decrease the incidence of graft rejection. Some institutions use RBC transfusion for this purpose. It is reported that transfusion therapy depresses natural killer cell function in these patients but the T4/T8 cell ratio remains normal. In addition, some studies report a somewhat greater incidence of recurrences or decreased overall survival in colon cancer patients who had multiple transfusions compared with those without transfusion, although this is disputed by other investigators.

  • Cytopenic Reactions

    Thrombocytopenia

    Blood platelets contain at least three antigen systems capable of producing a transfusion reaction. The first is the ABO (ABH) system, also found on RBCs; for that reason the AABB recommends that single-donor platelet units be typed for the ABO group before being transfused. Platelets do not contain the Rh antigen; however, since platelet units may be contaminated by RBCs, it is safer to type for D (Rho) antigen in addition to ABO typing. The majority of investigators believe that ABO-Rh typing is useful only to avoid possible sensitization of the recipient to RBCs and that recipient anti-A or anti-B antibody will not destroy ABO-incompatible platelets. There are platelet-specific antigens (PLA1 group, also called Zwa, and several others) that are found in high incidence and thus rarely cause difficulty. However, PLA1 antibodies have been implicated in a syndrome known as posttransfusion purpura (Chapter 8). Finally, there is the class I HLA-A,B,C group. This tissue compatibility system has been incriminated in patients who become refractory to repeated platelet transfusions (i.e., in whom the platelet count fails to rise) and in those who develop a febrile reaction after platelet administration. Interestingly, it has been reported that there is not a good correlation between the number of platelet transfusions and development of HLA antibodies. Persons who are HLA-compatible (usually siblings) as a rule are able to donate satisfactorily. The HLA-A antigens are also present on WBCs. Finally, other types of antiplatelet antibodies may appear, such as those of chronic idiopathic thrombocytopenia. In this situation, transfused platelets are quickly destroyed, making the transfusion of little value unless the patient is actively bleeding (Chapter 10).

  • Allergic Reactions

    Allergic reactions are the second most common transfusion reaction. They are presumably due to substances in the donor blood to which the recipient is allergic. Symptoms are localized or generalized hives, although occasionally severe asthma or even laryngeal edema may occur. There is usually excellent response to antihistamines or epinephrine.

  • Nonhemolytic Febrile Reactions

    Sometimes called simply (and incorrectly) “febrile reactions,” nonhemolytic febrile reactions occur in about 1% (range, 0.5-5.0%) of all transfusions, more commonly in multiply transfused patients.

    Leukoagglutinin reaction. The most common variety of nonhemolytic febrile reaction and the most common of any transfusion reaction is a febrile episode during or just after transfusion due to patient antibodies against donor leukocytes (leukoagglutinins). Before leukoagglutinins were recognized, these episodes were included among the pyrogenic reactions (discussed later). Fever may be the only symptom but there may be others, such as chills, headache, malaise, confusion, and tachycardia. In a small number of cases a syndrome known as transfusion-related acute lung injury is produced. It includes febrile reaction symptoms plus dyspnea and tachycardia; the chest x-ray film has a characteristic pattern described as numerous hilar and lower lobe nodular infiltrates without cardiac enlargement or pulmonary vessel congestion. In some cases the clinical picture includes marked hypoxemia and also hypotension and thus strongly resembles the adult respiratory distress syndrome. However, symptoms usually substantially improve or disappear in 24-48 hours (81% of patients in one report), but the radiologic abnormalities may persist for several days. Some patients have eosinophilia, but others do not. The syndrome has been called “noncardiac pulmonary edema,” a somewhat unfortunate term since pulmonary edema is not present, although many clinical findings simulate pulmonary edema. Most cases with leukoagglutinin lung involvement follow transfusion of whole blood. At least some of these reactions have been traced to histocompatibility leukocyte antigen (HLA) system incompatibility.

    Most patients produce leukoagglutinins due to previous transfusion or from fetal antigen sensitization in pregnancy. The more transfusions, the greater the likelihood of sensitization.

    Reactions due to leukoagglutinins are usually not life threatening but are unpleasant to the patient, physician, and laboratory. Since clinical symptoms are similar to those of a hemolytic reaction, each febrile reaction must be investigated to rule out RBC incompatibility, even if the patient is known to have leukoagglutinins. Leukoagglutinin reactions may be reduced or eliminated by the use of leukocyte-poor packed RBC, washed RBC, frozen RBC, or best, use of a special leukocyte-removal filter (Chapter 10). There are specialized tests available that are able to demonstrate leukoagglutinin activity, but most laboratories are not equipped to perform them. The diagnosis, therefore, is usually a presumptive one based on history and ruling out hemolytic reaction.

    Washed or frozen RBCs contain fewer white blood cells (WBCs) than the average leukocyte-poor packed cell preparation. However, since washed or frozen RBCs must either be transfused within 24 hours after preparation or be discarded, one must be certain that a need for transfusion exists sufficient to guarantee that the blood will actually be administered before these blood products are ordered. In contrast, leukocyte filtration can be done at the patient’s bedside as part of the transfusion.

    Pyrogenic reactions. These result from contamination by bacteria, dirt, or foreign proteins. One frequently cited study estimates that nearly 2% of donor blood units have some degree of bacterial contamination, regardless of the care taken when the blood was drawn. Symptoms begin during or shortly after transfusion and consist of chills and fever; the more severe cases often have abdominal cramps, nausea, and diarrhea. Very heavy bacterial contamination may lead to shock. Therefore, in a patient with transfusion-associated reaction that includes hypotension, a Gram-stained smear should be made from blood remaining in the donor bag without waiting for culture results.

  • Jaundice in the Newborn or Neonate

    Current consensus criteria indicating pathologic rather than physiologic levels of total bilirubin are the following:

    1. Total bilirubin level over 5 mg/100 ml (88 µmol/L) in the first 24 hours.
    2. Total bilirubin level over 10 mg/100 ml (171 µmol/L) during the second day of life, or an increase of 5 mg/100 ml per day or more thereafter.
    3. Total serum bilirubin level more than 15 mg/100 ml in full-term neonates.
    4. Total serum bilirubin level more than 12 mg/100 ml in premature neonates.
    5. Persistence of jaundice after the first 7 days of life.
    6. Conjugated bilirubin level over 1.5 mg/100 ml at any time.

    A number of conditions in addition to hemolytic disease of the newborn may be associated with elevated bilirubin; some of these conditions include bacterial sepsis, cytomegalovirus or toxoplasma infection, glucose 6-phosphate dehydrogenase deficiency, and resorption of heme from cephalhematoma or extensive bruising. These are uncommon causes of jaundice. Other factors that may increase total bilirubin are the following:

    1. Breast feeding. Although this subject is controversial, a number of studies have found an average increase of about 1.5 mg/100 ml and individual increases up to 2 mg/100 ml or even 3 mg in breast-fed neonates compared to bottle-fed neonates.
    2. Race. In one study, Asian neonates had a 31% incidence of nonphysiologic total bilirubin levels after the first day, compared to 20% in Hispanics, 14% in Europeans, and 9% in African Americans.
    3. Maternal smoking. This is associated with mildly lower infant bilirubin values.
    4. Weight loss and caloric deprivation. These increase serum bilirubin values in both children and adults.
    5. Prematurity. Neonates weighing less than 2,000 gm at birth are on the average about 3 times as likely to develop serum total bilirubin levels over 8 mg/1000 ml and those between 2000-2500 gm are twice as likely to develop such levels as infants with normal birth weight of 2500 gm or more. For bilirubin levels of 14 mg/100 ml, the likelihood is 8 times for the lowest birth rate category and 3 times for the intermediate category.

    Total bilirubin in neonates is almost all nonconjugated, with the conjugated fraction being less than 0.5 mg/100 ml. Elevated conjugated bilirubin level suggests sepsis, liver or biliary tract disease, or congenital abnormality of bilirubin metabolism such as Rotor’s syndrome. However, the level of conjugated bilirubin partially depends on the combination of assay methodology, reagents, and equipment used. Proficiency test surveys such as those of the College of American Pathologists shows that most laboratories have similar results for total bilirubin. For conjugated bilirubin, however, results on a specimen with elevated nonconjugated bilirubin (such as a normal newborn) show normal conjugated bilirubin in some laboratories, significantly elevated conjugated bilirubin in another group of laboratories, and levels between those of the first two groups in a third group of laboratories. Most of the higher and intermediate values were performed on automated chemistry equipment. In my own laboratory, using a well-known automated chemistry analyzer called the Abbott Spectrum, we were in the group with false high values compared to the normal group and the group with intermediate elevated values. Our upper limit of the reference range for conjugated bilirubin on clinically normal adults is 0.4 mg/100 ml. In a study done on newborns with total bilirubin levels ranging from 2-25 mg/100 ml, the Spectrum reported conjugated bilirubin elevations up to 1.2 mg/100 ml when total (nonconjugated) bilirubin was elevated. Surprisingly, once the level of 1.2 mg/100 ml was reached, it would not increase further regardless of further increase in total bilirubin. Therefore, the Spectrum includes some nonconjugated bilirubin in its conjugated bilirubin assay up to a certain point. The majority of laboratories show this phenomenon to some degree. Therefore, for these labs, the reference range upper limit for conjugated bilirubin must be readjusted when the total bilirubin level is elevated.