There was 100% agreement between enzyme immunoassay (EIA) (Abbott Laboratories), Western blot, and indirect immunofluorescence (IF) when these three methods were used to measure antibody to the acquired immune deficiency syndrome (AIDS) virus in sera from 142 high-risk individuals, indicating that IF was a sensitive alternative method for detecting antibody to this agent. Thirty-two (64%) of 50 EIA-positive plasma specimens from a blood bank and 6 (21%) of 28 EIA-positive sera from alternative testing sites were negative by IF. In addition, two EIA-negative sera from the latter group were positive by IF. Western blotting agreed with IF on those 40 specimens which gave discrepant results by EIA and IF. The IF method was determined to be equal to Western blotting in sensitivity and specificity for detection of AIDS antibody, and it was found to be useful for confirming positive EIA results, especially in specimens from individuals in low-risk groups.

Results by an enzyme immunoassay method (EIA) performed at one serum dilution and results by indirect immunofluorescence (IFA) and hemagglutination inhibition (HI) tests performed at step dilutions were correlated with results by a neutralization test (50% plaque neutralization [PN]) performed at step dilutions on single serum samples for serologic evaluation of immunity status to measles virus. PN results were taken as true indicators of immunity, and the other tests were evaluated on that basis. The predictive value of a positive result being positive also by PN was 95.3% for HI and 93.3% for EIA and IFA. The predictive value of a negative result being negative also by PN was 81.1% for HI, 100% for EIA, and 75.0% for IFA. A similar study on immunity status to varicella-zoster virus by EIA and by an anticomplement immunofluorescence test versus PN showed a 100% predictive value of a positive or negative result by EIA. By the anticomplement immunofluorescence test, the predictive value of a positive result was 97.7%, and that of a negative result was 88.5%. Studies on the comparative ability of EIA versus complement fixation (CF) to detect significant changes in antibody concentration between acute-phase and convalescent-phase serum samples indicative of a current infection were also done. Both tests were satisfactory for the serodiagnosis of measles or varicella-zoster virus infections. However, EIA was preferable to CF because it was less technically difficult, less labor intensive, and could be performed on sera that were anticomplementary in CF reactions.

Antibodies to different cytomegalovirus (CMV) polypeptide antigens, captured by monoclonal antibodies coated on the solid phase of an enzyme immunoassay test, were analyzed in 42 serum pairs submitted for serodiagnosis of CMV infection. Three CMV antigens, captured on the solid phase by three monoclonal antibodies of different specificities, designated CH92-1, CH65-1, and CH16-1, were glycoproteins A (gA), gC, and gD, respectively; and one antigen, captured by CH23, was a polypeptide with an apparent molecular weight of 150,000, possibly associated with the nucleocapsid. Of these four CMV antigens, gA captured by CH92-1 was most effective in eliciting an antibody response. Antibody to this antigen was present in serum samples at a higher concentration in primary and reactivated infection and persisted longer than did antibody to the other tested antigens. In contrast, antibody to antigen captured by CH23 was at a lower concentration, rose more slowly in infection, and persisted for a shorter time than did antibody to the other antigens. Antibody response to gC and gD was intermediate in concentration and temporal appearance compared with the antibody response to gA and to the polypeptide bound by CH23. An enzyme immunoassay on paired serum samples with the captured glycoproteins as antigen was equal for the detection of current infection to an enzyme immunoassay with the whole CMV antigen from infected cell lysates. Enzyme immunoassays with either the CMV glycoproteins or the whole CMV antigen from infected cell lysates were superior to a complement fixation test with a glycine extract antigen for serodiagnosis of current infection.

Several methods for evaluating and reporting enzyme immunoassay (EIA) determinations of antibody to herpes simplex virus derived from one dilution of single serum samples were studied. An EIA ratio method for serological evidence of current infection from paired serum samples was also evaluated. Optical density (OD) of the reaction at a 1:100 serum dilution and estimated titers obtained by reference of the OD of the serum dilution to a standard curve were compared to the corresponding plotted EIA titer obtained by titration to endpoint. Neither the OD per se nor the estimated titer was completely predictive of the plotted titer (correlation coefficient [r] of 0.824 and 0.817, respectively), and they provided only a semiquantitative measurement of antibody concentration. For an antibody status report, however, OD would be sufficient if related to the cutoff value as an EIA index (OD of sample divided by cutoff OD for positive specimens). The OD of the EIA reaction at a single dilution (1:5) of cerebrospinal fluid, on the other hand, correlated quite well with the titer obtained by titration (r = 0.950). For serological diagnosis of current infection, the OD ratio of convalescence-phase/acute-phase sera was determined at several dilutions. A ratio of greater than or equal to 1.54 was calculated as a reliable index for a significant rise in antibody concentration and compatible with current infection. By determining the convalescent-phase/acute-phase serum ratio at two dilutions, 1:100 and 1:1,000, the EIA ratio method appeared to be a sensitive as or more sensitive than, complement fixation in diagnosing current infection.

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