Clinical evaluation of a new recombinant antigen-based cytomegalovirus immunoglobulin M immunoassay in liver transplant recipients.

BACKGROUND: Human cytomegalovirus (CMV) is a significant cause of morbidity and mortality among transplant recipients. Monitoring transplant recipients by CMV IgM serology has been questioned by several studies due to the reported insensitivity of serologic tests relative to antigen detection methods. METHODS: In this retrospective study, we have evaluated the performance of the new recombinant antigen-based Abbott AxSYM CMV IgM assay and compared it with CMV culture technique in a cohort of 40 liver transplant recipients who did not receive antiviral prophylaxis. RESULTS: The sensitivity, specificity, and positive and negative predictive values for detection of CMV disease by the AxSYM CMV IgM assay were 90.0%, 60.0%, 69.2%, and 85.7%, respectively, and by culture the values were 100%, 55.0%, 69.0%, and 100%, respectively. Detection of CMV IgM occurred before or at the time of CMV disease in only R+ recipients. CONCLUSION: Although this assay is a sensitive test for CMV-specific IgM, detection of CMV IgM preceded detection of virus by culture in patients only when the liver transplant recipient was CMV immune before transplantation (R+).

Clinical comparison of the Treponema pallidum CAPTIA syphilis-G enzyme immunoassay with the fluorescent treponemal antibody absorption immunoglobulin G assay for syphilis testing.

Recently, a treponema-specific immunoglobulin G (IgG) enzyme immunoassay (EIA), the CAPTIA Syphilis-G (Trinity Biotech, Jamestown, N.Y.), has become available as a diagnostic test for syphilis. A total of 89 stored sera previously tested by the fluorescent treponemal antibody absorption (FTA-ABS) IgG assay were evaluated by the CAPTIA EIA. The FTA-ABS IgG procedure was performed by technologists unblinded to results of rapid plasmid reagin (RPR) testing of the same specimens. Borderline CAPTIA-positive samples (antibody indices of >/=0.650 and 0.900, the sample was considered positive. Thirteen of 89 (15%) samples had discrepant results. Compared to the FTA-ABS assay, the CAPTIA EIA had a sensitivity and specificity and positive and negative predictive values of 70.7, 97.9, 96.7, and 79.7%, respectively. In another analysis, discrepancies between results were resolved by repeated FTA-ABS testing (technologists were blinded to previous RPR results) and patient chart reviews. Seven CAPTIA-negative samples which were previously interpreted (unblinded) as minimally reactive by the FTA method were subsequently interpreted (blinded) as nonreactive. One other discrepant sample (CAPTIA negative and FTA-ABS positive [at an intensity of 3+], unblinded) was FTA negative with repeated testing (blinded). For the five remaining discrepant samples, chart reviews indicated that one patient (CAPTIA negative and FTA-ABS positive [minimally reactive], blinded) had possible syphilis. These five samples were also evaluated and found to be negative by another treponema-specific test, the Treponema pallidum microhemagglutination assay. Therefore, after repeated testing and chart reviews, 2 of the 89 (2%) samples had discrepant results; the adjusted sensitivity, specificity, and positive and negative predictive values were 96.7, 98.3, 96.7, and 98.3%, respectively. This study demonstrates that the CAPTIA IgG EIA is a reliable method for syphilis testing and that personnel performing tests which require subjective interpretation, like the FTA-ABS test, may be biased by RPR test results.

Blood volume determination as a function of hematocrit and mass in three preservative solutions and saline.

Accurate blood volume determination is useful both clinically and in research. In many instances, however, direct measurement of blood volume is impractical due to the risk of bacterial contamination. For this reason, mass is often used to estimate volume. The relationship between mass and volume (density) varies with different suspension solutions and hematocrits. In this paper, equations are derived to calculate volume as a function of hematocrit and mass for pooled red cells suspended in four solutions: CPD plasma (whole blood), additive solutions 1 and 3 (AS-1 and AS-3), and saline. To validate this approach, the actual versus predicted blood volumes in 10 individual blood samples suspended in either AS-1 or saline are compared. The equations predict the volume of blood to within 0.5% and 1.0% in samples with low/normal and high hematocrits (15% to 85%, respectively). Use of these equations allow for accurate and rapid conversion of mass to volume for these blood products.

Rejuvenation of erythrocytes preserved with AS-1 and AS-3.

Rejuvenation of erythrocytes (biochemical modification of adenosine triphosphate and 2,3-diphosphoglycerate) preserved with currently available nutrient additive solutions has not been licensed or adequately studied. The ability of the commercially available solution PIPA to modify erythrocytes preserved with AS-1 or AS-3 for 35 and 42 days was studied. Use of PIPA produced greater-than-normal levels of adenosine triphosphate in the preserved erythrocytes. Restoration of 2,3-diphosphoglycerate was suboptimal at both periods. (PIPA treatment produces normal levels of 2,3-diphosphoglycerate in erythrocytes preserved for 35 days with citrate-phosphate-dextrose-adenine-1.) In erythrocytes preserved with AS-1 or AS-3 for 42 days, 2,3-diphosphoglycerate returned to normal levels after a second PIPA rejuvenation. This study demonstrates that biochemical modification is possible in erythrocytes preserved with AS-1 or AS-3 for 42 days.

In vivo viability and functional integrity of filtered platelets.

The in vivo viability and functional integrity of filtered platelets were compared with those of nonfiltered platelets in a controlled study. On two occasions, after template bleeding time, 14 healthy volunteers underwent plateletpheresis and received 600 mg of aspirin. Autologous 111In-labeled platelets were transfused without further manipulation (control) on one occasion and after filtration on a second occasion. The filter was primed and flushed with a buffered 12.6-percent solution of ACD-A in 0.9-percent normal saline (pH 6.5). After transfusion, the bleeding time was measured at 1, 4, and 24 hours and platelet survival at 10 minutes; 1, 4, and 24 hours; and daily for 6 days. The decrease in the bleeding time was not significantly different from that after transfusion of nonfiltered platelets (p greater than 0.2). Filtering of platelets did not affect 1-hour in vivo recovery (filtered, 69.5%; nonfiltered, 66%: p = 0.56) or the platelet survival (filtered platelet t1/2 = 83.0 hours, nonfiltered platelet t1/2 = 82.9 hours: p = 0.96). It can be concluded that filtration does not adversely affect in vivo recovery, survival, or functional integrity of platelets.