Antibodies to co-trimoxazole (trimethoprim and/or sulfamethoxazole) related to the presence of the drug in a commercial low-ionic-strength solution

BACKGROUND: Drug‐dependent antibodies have been associated with approximately 10% of acquired immune hemolytic anemia cases. These antibodies are a rare cause of interference in pretransfusion red blood cell (RBC) serologic testing. The aim of this work was to report three cases of subjects developing antibodies against co‐trimoxazole, a combination of trimethoprim (TMP) and sulfamethoxazole (SMX). CASE REPORT AND METHODS: Blood samples of donor/patients were referred to our laboratory for the exploration of a positive antibody detection test. There was no recent history of drug taking. Antibody identification was performed by gel test using an indirect antiglobulin test, with reagent RBCs in low‐ionic‐strength solutions (LISS) containing co‐trimoxazole or not. RESULTS: All three sera showed positive reactions when RBCs were resuspended in LISS containing co‐trimoxazole, but negative reactions when RBCs were resuspended in LISS without antibiotic. We detected antibodies against co‐trimoxazole showing three different antibody patterns: anti‐TMP plus anti‐SMX, anti‐TMP alone, or anti‐SMX alone. Anti‐TMP showed an apparent anti‐Ku specificity in the two cases where it was present. Anti‐SMX showed an apparent anti‐H specificity in one of the two cases described. The drug‐dependent antibodies were not associated with acquired hemolytic anemia or other pathologies. CONCLUSION: Antibodies against co‐trimoxazole may only be detected when using a diluent for reagent RBCs containing the drug in question. Antibody pattern (anti‐TMP and/or anti‐SMX) may vary according to individuals' immune response. Drug‐dependent antibodies may react as antibodies against a high‐prevalence antigen, supporting the hypothesis of antibodies to drug and membrane components. Drug‐dependent antibodies such as anti‐co‐trimoxazole may be a serologic finding without clinical features.     

A proposal for compatibility testing incorporating the manual hexadimethrine bromide (Polybrene) test

In November 1984, the Standards Committee of the American Association of Blood Banks changed the requirements for pretransfusion testing by making the performance of an antiglobulin crossmatch optional when the antibody screening test is negative. The crossmatch would be necessary only to confirm ABO compatibility. Many will welcome this change; others will persist in their current methods. This article presents data supporting the use of the manual hexadimethrine bromide (Polybrene) test, a 1-minute room temperature procedure, as a crossmatch technique when the antibody screening test is negative. The manual Polybrene test (MPT) is an effective method for detecting ABO incompatibility. Forty-seven randomly selected serums gave expected results with A1, A2, and B red cells. Only 66 percent of 84 group B sera were serologically incompatible with A2B red cells by MPT, but the same results (69% positive) were observed using a 5-minute low-ionic-strength solution (LISS) room temperature technique. As only 37 percent of these crossmatches were incompatible using a LISS immediate spin (IS) method, the reliability of an IS method is questioned. An MPT crossmatch provides added security in that most unexpected blood group antibodies are demonstrable by this method. Of 106 serums tested which contained antibodies, 83 reacted. We believe that the MPT provides a rapid and sensitive test that, accompanied by a carefully performed antibody screening test, meets the requirements of Standards and will provide for safe red cell transfusion without the need for an antiglobulin crossmatch.     

Evaluation of the polyethylene glycol-indirect antiglobulin test for routine compatibility testing

All specimens received in the blood bank over a 5-month period for crossmatch or group and screen requests were tested in parallel by a polyethylene glycol-indirect antiglobulin test (PEG-IAT) and a low-ionic-strength saline (LISS)-IAT. The sera of 41 of 1471 patients had reactions, with 50 antibodies being detected. Ten antibodies reacted only on the PEG-IAT and 14 only by the LISS-IAT; the remaining 26 antibodies were detected by both methods. Of the antibodies that reacted only by the LISS-IAT, one (anti-Jka) was considered clinically significant, whereas five of the antibodies that reacted only by the PEG-IAT (1 anti-c, 2-Fya, 1-Jkb, and 1-S) were considered significant. Two antibodies of questionable clinical significance were detected only by the PEG-IAT. In 97 percent of the sera tested, no reaction was detected by either method. The PEG-IAT is an acceptable technique for routine compatibility testing.     

Comparison of low ionic diluents for use with the Diamed antiglobulin gel test

Microtube column systems, although widely used in transfusion serology for the detection of red cell antibodies, may not detect weak Fy(a), Jk(a), S and K antibodies. A number of low ionic diluents are used to shorten the incubation time required for red cell antibody detection in the antiglobulin test. However, there are no published reports to show whether these low ionic diluents vary in their ability to detect red cell antibodies using microcolumn detection systems. Three low ionic diluents, Diamed ID-CellStab, Diamed ID-Diluent2 and an in-house produced low ionic strength solution (LISS), were assessed using the Diamed-ID LISS/Coombs microtube column system (in accordance with the manufacturer's instructions), to ascertain whether the choice of diluent influences red cell antibody detection. Two hundred and seventy patient samples were screened for red cell antibodies. The reaction strength was increased in 50% of the samples with detectable red cell antibodies using LISS as the diluent compared with ID-CellStab. Of the 51 red cell antibodies directed against Rhesus, Duffy, Kidd or Kell antigens, 21% reacted more strongly in LISS compared with Diamed ID-CellStab with a difference in grading of > or =1. Minimal disparity was found between ID-Diluent2 and LISS. Biochemical analysis of pH, osmolality, sodium, potassium and phosphate were comparable for ID-CellStab, ID-Diluent2 and LISS. Measurement of conductivity in each low ionic diluent was performed as a measure of ionic strength in the final reactant mix, as the same amount of low ionic diluent was used for each test. The conductivity was 3 x 5 mS cm for LISS and ID-Diluent2, and 5 x 8 mS cm for ID-CellStab; the acceptable range being 3 x 7 +/- 0 x 3 mS cm as cited in the Guidelines for the Blood Transfusion Services in the United Kingdom. This evaluation suggests that ID-CellStab is a suboptimal low ionic diluent for red cell antibody detection using Diamed-ID LISS/Coombs gel cards. The poorer performance of ID-CellStab compared with LISS may be explained by its higher ionic strength.     

Comparison of a modified manual hexadimethrine bromide (Polybrene) and a low-ionic-strength solution antibody detection technique

Manual hexadimethrine bromide (Polybrene) tests (Polybrene in low-ionic medium) were used in parallel with manual low-ionic-strength solution (LISS) procedures for the routine testing of patient samples referred to a general hospital blood bank. Of 5646 consecutive sera tested, 5167 (91.5%) did not react with either technique; 320 sera (5.7%) reacted in both methods. The Polybrene technique detected 63 antibodies which did not react in the LISS methods. One hundred sera did not react in the Polybrene test, but did react in the LISS methods. Sera showing discrepant results between the two methods were further tested in a reference laboratory. Polybrene tests appeared to be better in avoiding reactions due to clinically nonsignificant antibodies. The LISS methods, however, appeared to be more sensitive in detecting antibodies of potential clinical significance.     

Comparison of plasma and serum for antibody detection using DiaMed microtubes

Atypical antibody detection in DiaMed microtubes using a low-ionic-strength saline (LISS) indirect antiglobulin technique (IAT) was assessed using both serum and plasma. During the first period of the study all atypical antibodies originally detected in serum were also detected in EDTA plasma with comparable reaction strengths. Two of 73 antibodies were not detected in citrated plasma.   During the second period of the study all routine antibody screens were performed in both serum and EDTA plasma. More clinically significant antibodies were detected in EDTA plasma than in serum. More false positives and non-specific antibodies were also detected in EDTA plasma. It is concluded that EDTA plasma is a suitable medium for antibody detection using LISS IAT in DiaMed gel microtubes.     

Monocyte monolayer assay (MMA) reactivity of alloantibodies reacting by the manual polybrene technique but not by an antiglobulin test

SUMMARY. The manual polybrene technique (MP) has been shown to be useful in pretransfusion testing as a rapid method capable of detecting a wide range of red cell antibodies. The clinical significance of alloantibodies reacting by the MP but not by an antiglobulin test (MP +/AGT-) has not been determined.
The monocyte monolayer assay (MMA) is an established in vitro technique for assessing the likely clinical significance of red cell antibodies. This was used to examine 21 MP +/AGT- alloantibodies and 41 alloantibodies reacting by a LISS antiglobulin method (LISS-AGT).
Two of the 21 MP +/AGT- antibodies (9.5%) produced positive results by the MMA compared with 26/41 (63.4%) of LISS-AGT-reactive antibodies. The incidence of positive reactivity of the latter antibodies in the MMA was similar between those that were reactive and nonreactive by the MP.
These results suggest that antibodies reacting by MP and not by an antiglobulin test are less likely to be clinically significant.     

Comparison of a commercial hexadimethrine bromide method and low-ionic- strength solution for antibody detection with special reference to anti- K

The sensitivities of manual low-ionic hexadimethrine bromide (Polybrene, LIP) and low-ionic Polybrene indirect antiglobulin tests (LIPAT) were compared with those of a manual low-ionic-strength indirect antiglobulin test (LISS) by using a commercial Polybrene kit. One hundred antibodies were coded, titrated, and tested in parallel. LIP did not detect 36 antibodies: 31 anti-K, two anti-E, two anti-Fya, and one anti-Jka. LIPAT did not detect seven anti-K, two anti-E, and two anti-Jka. The combination of LIP and LIPAT did not detect two anti-E that were reactive only in a two-stage enzyme test and seven anti-K that had titers of 2 or lower by LISS. LISS detected all antibodies except for the two enzyme-reactive anti-E. There were no significant differences in the titers of 63 percent of the antibodies studied. For 54 percent of the antibodies in the Kell system, LISS produced significantly higher titers; for 25 percent of antibodies in the Rh system, LIP did so. The poor sensitivity of the Polybrene kit for anti-K makes it unsuitable as a primary method for antibody screening.     

An acute hemolytic transfusion reaction caused by an anti-P1 that reacted at 37 degrees C

BACKGROUND: Hemolytic transfusion reactions (HTRs) due to anti-P1 have rarely been reported. There is only one report (from 1945) of an acute HTR due to anti-P1. CASE REPORT: A 74-year-old woman with anti-P1 was given blood that had been found to be compatible by the use of prewarmed serum and saline-suspended red cells (RBCs) and of an antiglobulin test with anti-IgG. The test mixtures were not centrifuged or inspected for agglutination after the 37 degrees C incubation phase. After transfusion of 50 mL of P1 + blood, the patient had an acute HTR (hemoglobinemia, hemoglobinuria, and increased blood pressure, temperature, and respiration). RESULTS: When studied by a reference laboratory, the anti-P1 was shown to be easily detectable (3+ agglutination) by a prewarming technique (saline or low-ionic-strength saline [LISS]), which included centrifugation at 37 degrees C, but only weak reactions were observed when centrifugation after 37 degrees C incubation was omitted. The indirect antiglobulin test was weakly positive (1+) with anti-IgG, but polyspecific anti-human globulin reacted 2+. The anti-P1 agglutinin was IgM, and its titer was 16 at 37 degrees C (prewarmed) and 256 at 23 degrees C; it caused hemolysis of RBCs at 37 degrees C under conditions known to enhance hemolysis. An indirect monocyte monolayer assay gave results of 11.2 and 22 percent in testing of P1 + RBCs incubated with the patient's serum alone and with patient's serum plus fresh normal serum (as a source of complement), respectively (normal < or = 3%). CONCLUSION: An acute HTR was caused by a hemolytic anti-P1 that reacted at 37 degrees C. This antibody was not detected by the hospital in a prewarmed crossmatch that omitted 1) the addition of LISS, 2) the reading for agglutination after the 37 degrees C incubation, and 3) the use of antiglobulin sera containing anti-complement.     

Frequency of delayed hemolytic transfusion reactions following antibody screening and immediate-spin crossmatching

In view of the continuing controversy regarding the use of immediate-spin crossmatch procedures in preparing blood for transfusion to patients in whom unexpected clinically significant antibodies have not been found by antibody screening by the indirect antiglobulin test (IAT), a review of 8 years' experience with such a policy was conducted. In that period, 54,725 units of packed red cells or whole blood were transfused to 10,146 patients. Four clinically overt delayed hemolytic transfusion reactions and 18 clinically silent delayed serologic transfusion reactions were found. In 3 of the 22 patients, the offending antibody(ies) were detectable in the pretransfusion serum by an enzyme IAT, but none was detectable by routine saline IAT against either a three-cell screening panel or the transfused cells. Thus, the incorporation of saline indirect antiglobulin crossmatch would not have prevented the delayed reactions. It can be concluded that the use of a saline indirect antiglobulin crossmatch offers no significant advantage over the current policy of using only immediate-spin crossmatch for those patients whose pretransfusion serum gives negative results in a three-cell screen using a saline IAT.     

A LISS spin enzyme method for the detection of red cell antibodies and its use in routine antibody screen procedures

A technique for performing the enzyme phase of the antibody screen on red cells suspended in low-ionic-strength-salt solution (LISS) is described. The reliability of this LISS spin-enzyme (LSE) technique was compared with the two-stage papain-tile method, in the detection of 62 previously identified enzyme reacting antibodies. All 62 antibodies examined were detected by the LSE method, and no false-positive reactions were found. Using LSE and papain-tile methods in parallel, further assessment was obtained by screening 2000 sequential blood samples under routine service conditions. Fifty-six blood samples contained alloantibodies, of which 43 reacted by both methods, eight by the LSE method only, and five by the papain-tile method only. It was concluded that the LSE method was comparable to the papain-tile method.     

Application of noninvasive phagocytic cellular assays using autologous monocytes to assess red cell alloantibodies in sickle cell patients.

We investigated red cell (RBC) alloantibodies in 125 sickle cell anemia (SCA) patients using tube indirect antiglobulin test (PEG, LISS or enzyme) and gel centrifugation test (LISS or enzyme). Prediction of clinical significance of alloantibodies was evaluated by the monocyte monolayer assay (MMA) and the chemiluminescence test (CLT) using autologous monocytes. The alloimmunization rate was 20.8% and the gel test detected a higher number of alloantibodies than the tube test (26 v 21, p = 0.02). We observed 58.3% and 69.2% positive MMA and CLT results, respectively. Eighteen (69.2%) antibodies exhibited clinical relevance, 14 (58.3%) antibodies reacted by both MMA and CLT, while 4 (15.4%) antibodies reacted only by CLT. In conclusion, the application of phagocytic cellular assays using autologous monocytes defined clinical significance of about 70% of RBC alloantibodies detected in SCA patients. The data also suggest that the CLT may be more valuable than the MMA as a noninvasive test for predicting hemolysis after transfusion of incompatible blood in SCA patients.     

Comparative sensitivity of solid phase versus PEG enhancement assays for detection and identification of RBC antibodies.

Blood banks require a sensitive, specific, and efficient method to detect clinically significant RBC antibodies. Solid phase antibody screening methods are popular due to high sensitivity and automation. However, the high degree of reactivity detects "false positive" antibodies of questionable clinical significance leading to additional testing. We studied positive rates of Capture-R vs. PEG methods and categorized RBC antibodies identified by initial test results of 33,564 consecutive samples by Capture-R method. Capture-R was positive in 1,084/33,564 (3.2%) of samples. Using PEG as our "gold standard", PEG confirmed true positivity (i.e., > or = 1 cell reacting) in 710 Capture-R positive samples (65.5%); 374 Capture-R positive samples (34.5%) did not react in PEG (i.e., false positives). Of the 710 samples with true positivity, only 510 showed clinically significant alloantibodies. Using PEG as our "gold standard", only 2/3 of reactions by Capture-R were considered true positives. Because of ease and automation, Capture-R is popular as a screening test, but a more specific method may be helpful in order to identify truly significant alloantibodies.     

Clinical significance of the anti-complement component of antiglobulin antisera

The need for anti-complement (anti-C') activity in antiglobulin antisera (AHG) for the detection of clinically significant antibodies was evaluated during a three-year period. While performing routine compatibility testing using standard blood banking procedures, eight patients were found whose antibodies were detectable primarily or only by AHG containing anti-C' activity; monospecific anti-igG AHG gave weak or negative reactions. Seven of the antibodies were anti-jka or jkb. Two of the anti-jka antibodies were responsible for clinically unsuspected delayed hemolytic transfusion reactions. The anti-jkb antibody resulted in a shortened survival of incompatible 51Cr-labelled red blood cells. The incidence of such "complement-only" Kidd antibodies was 23 percent of all Kidd antibodies found. These data suggest that the omission of anti-C' in AHG in routine compatability testing could result in substantial risk of failure to detect clinically significant antibodies.     

Comparison of the polyethylene glycol antiglobulin test and the use of enzymes in antibody detection and identification

BACKGROUND: The polyethylene glycol indirect antiglobulin test for detection of red cell antibodies was compared with a proven, highly sensitive test system using papain. STUDY DESIGN AND METHODS: Parallel, prospective testing of 1508 samples with polyethylene glycol and with albumin and papain evaluated the sensitivity and specificity of polyethylene glycol. Retrospective analysis of antibody specificities was performed for the 2 years before and the 2 years after the institution of polyethylene glycol testing. RESULTS: Of 1508 prospective screens, 53 (3.5%) had discordant results: 5 were positive only in polyethylene glycol and 48 were positive only in albumin and papain. Upon antibody identification, the 5 samples that were positive only in polyethylene glycol showed 1 anti-D, 2 warm autoantibodies, and 2 false-positive results. The 48 samples that were positive only in albumin and papain showed 1 each of the following: anti-Le(b); anti-P1; anti-S; high-titer, low-avidity antibody; and cold autoantibody; there were 43 false-positive results. False-positive results totaled 12 (0.8%) with polyethylene glycol and 53 (3.5%) with albumin and papain. The retrospective analysis of antibody specificity with polyethylene glycol showed a significant increase in the detection of Fy(a) and/or Fy(b) (p < 0.0002) and Jk(b) (p < 0.0002) antibodies and a decrease in the detection of Le(a) and/or Le(b) antibodies (p < 0.0002). CONCLUSION: Polyethylene glycol retained the high sensitivity of the albumin and papain, while significantly lowering the number of false- positive results and decreasing the detection of antibodies of doubtful clinical significance.     

Evaluation of immunohematologic routine methods using the new erythrocyte-magnetized technology on the QWALYS 2 system

BACKGROUND: QWALYS 2 is a fully automated system for ABO/D grouping, Rh phenotyping, K typing, and antibody screening (ABS). Its new erythrocyte-magnetized technology (EMT) is based on the use of magnetic nanoparticles and avoids centrifugation and washing steps.
STUDY DESIGN AND METHODS: Overall 499 blood samples were tested with our routine blood bank methods for ABO/D grouping, 313 samples for Rh phenotyping and K typing (microtiter plates; Olympus PK 7200), and 478 samples for ABS (gel centrifugation technique, DiaMed). All samples were tested in parallel with the EMT.
RESULTS: In 496 of 499 samples (99.4%), a complete concordance between the observed (QWALYS 2) and the expected results for ABO/D grouping was found. One sample with a weak A in an AB blood group and 2 samples with a weak D were not detected by the QWALYS system. Rh phenotyping and K tests revealed a 100% concordance. In the two ABS techniques, 427 samples were negative in both and 15 samples showed the same antibody specificity in both. Three immunoglobulin M antibodies were as expected negative in EMT and positive by DiaMed. In 32 cases (6.7%), false-positive reactions were observed by EMT due to 22 unspecific reactions (4.6%) and 10 lipemic or fibrinic plasmas (2.1%). One autoantibody was found by EMT only.
CONCLUSION: The EMT is reliably suited to ABO/D grouping, Rh phenotyping, and K testing and is suitable to detect immunoglobulin G red blood cell alloantibodies as well. The rate of false-positive reactions in ABS due to lipemic and fibrinic samples needs to be reduced.     

Validation of a hospital-laboratory workstation for immunohematologic methods

BACKGROUND: The FREELYS Nano system (Diagast) is a manual workstation for ABO/D grouping, Rh phenotyping, K typing, and antibody screening (ABS) for immunoglobulin G (IgG) antibodies only and works with the erythrocyte-magnetized technology (EMT). The principle of EMT is based on magnetization of red blood cells and avoids centrifugation and washing steps.
STUDY DESIGN AND METHODS: A total of 304 samples were tested with our routine blood bank methods, 100 samples for ABO/D grouping, 196 samples (100 at first evaluation, 96 at second evaluation) for Rh phenotyping and K typing (PK7200, Olympus), and 108 samples for ABS (DiaMed). All samples were tested in parallel with the FREELYS Nano.
RESULTS: We found a 100% concordance between the observed (FREELYS Nano) and the expected (Olympus PK7200) results for ABO/D grouping in all 100 samples. For Rh phenotyping and K tests, in 24 of 100 samples false-positive reactions were observed in the first evaluation by the FREELYS Nano. After changing the test kit batch for Rh phenotyping by the manufacturer, a complete concordance in Rh phenotyping and K tests was observed in a second evaluation. For ABS, the FREELYS Nano showed in 4 of 108 samples (3.7%) false-negative reactions for IgG antibodies (two anti-K, one anti-E, one anti-C^w), and one (0.9%) false-positive reaction.
CONCLUSIONS: The FREELYS Nano is reliably suited to ABO/D grouping, Rh phenotyping, and K testing. The rate of false-negative reactions for IgG antibodies should be reduced.     

Optimizing pretransfusion antibody detection and identification: a parallel, blinded comparison of tube PEG, solid-phase, and automated methods

BACKGROUND: The ideal pretransfusion testing strategy identifies maximal significant antibodies at minimal cost. Objectives of this study were to compare the characteristics of three testing methods and determine their optimal incorporation into the following generic testing sequence: 1) screen, for antibodies 2) if results are positive, use primary identification method, 3) if results are inconclusive, use secondary identification method. STUDY DESIGN AND METHODS: A total of 2000 consecutive, unselected, coded specimens were tested with three screening methods-PEG IAT, manual and automated solid phase red cell adherence assay (SPRCA). Of 202 positive results, 187 were of sufficient volume and were tested with both PEG and manual SPRCA identification panels, yielding 82 with significant antibodies, plus one that was negative by both methods found on retrospective review of nonstudy results. Calculations were made on the 1985 volume-sufficient specimens, simulating the possible testing permutations. RESULTS: Manual SPRCA was the most sensitive antibody screen (67/83 = 81%) and the least specific (1840/1902 = 97%); automated SPRCA was the least sensitive (54/83 = 65%) and most specific (1883/1902 = 99%); and PEG was intermediate in both sensitivity (64/83 = 77%) and specificity (1860/1902 = 98%). Of the identification panels, manual SPRCA identified more antibodies than PEG (67 versus 66) but had more inconclusive results (41 versus 20). Of overall strategies, manual SPRCA screening with either sequence of identification methods identified the most antibodies (66). The combination of PEG screen, PEG identification, and manual SPRCA identification identified slightly fewer antibodies (63) but had the lowest reagent cost, total (reagent plus labor) cost, and cost per antibody identified. The sequence of automated SPRCA screening with manual SPRCA identification, and PEG identification had the lowest hands-on time. CONCLUSIONS: The most cost-effective pretransfusion strategy is PEG screen with PEG identification, plus manual SPRCA identification when PEG identification is inconclusive.     

The detection by enzyme-linked immunosorbent assays of non-complement- fixing HLA antibodies in transfusion medicine

BACKGROUND: Noncomplement-fixing white cell antibodies have been demonstrated by the use of immunofluorescence flow cytometry against intact lymphocytes. However, such antibodies may be either HLA-specific or directed against other white cell antigens. Commercial enzyme-linked immunosorbent assay (ELISA) kits, using solubilized HLA molecules as targets, enable such HLA-specific antibodies to be detected in patients who are refractory to platelet transfusion, patients experiencing febrile transfusion reactions, and patients whose sera give nonspecific hemagglutination in indirect antiglobulin tests. STUDY DESIGN AND METHODS: Sera from all three groups of patients, previously screened for cytotoxic antibodies by using complement-dependent lymphocytotoxicity, were re-investigated with commercial ELISA kits for HLA antibody screening and identification using the manufacturers' recommended test methods. RESULTS: Non-complement fixing HLA antibodies were detected by ELISA in many sera that were lymphocytotoxicity test- negative; that is, 14 (17.5%) of 80 from refractory patients, 8 (23.5%) of 34 from those with febrile reactions, and 11 (22.4%) of 49 from those with nonspecific hemagglutination in the direct antiglobulin test. However, not all cytotoxic white cell antibodies were detectable by ELISA: only 19 (82.6%) of 23, 19 (67.8%) of 28, and 11 (73.6%) of 49, respectively in the three groups. Similarly, only 143 (79.4%) of 181 cytotoxic sera with clear-cut HLA-A or -B locus specificities were detectable by ELISA. CONCLUSION: ELISAs detect some but not all clinically significant HLA antibodies, irrespective of their ability to fix complement in vitro.     

The sensitivity and specificity of the immediate-spin crossmatch

The immediate-spin (IS) crossmatch is used to detect ABO incompatibility between donor red cells (RBCs) and the serum of the intended recipient. However, this test may be positive in the absence of ABO incompatibility (false positive) or it may be negative when ABO incompatibility exists (false negative). During a 25-month study, the rates of both false-positive and false-negative IS crossmatch results were evaluated, and the sensitivity and specificity of the IS crossmatch were determined. During the study period, 53,656 IS crossmatches were performed for patients without significant RBC antibodies. Fifty-five patients had positive IS crossmatches, and no false-negative reactions were found. In tests of 55 patients with positive IS crossmatches, 77 false-positive and 5 true-positive reactions were noted. The causes of the false-positive reactions were rouleaux (36 patients), cold-reactive antibodies (8 patients), a combination of rouleaux and cold-reactive antibodies (2 patients), fibrin clot (1 patient), and undetermined (3 patients). The sensitivity and specificity of the IS crossmatch were 100 and 99.86 percent, respectively. Laboratory personnel should be aware that the IS crossmatch may have false-positive or false-negative results, and they should develop written protocols to distinguish quickly between true-positive and false-positive reactions.