Hemadsorption immunosorbent technique for determination of rubella immunoglobulin M antibody.

A highly specific and sensitive hemadsorption immunosorbent technique for measuring rubella immunoglobulin M (IgM) antibody is described. IgM from human sera was absorbed into anti-human IgM-coated wells in plates and rubella-specific IgM was detected by adding rubella virus hemagglutinin and a small quantity of sheep erythrocytes. Centrifugation of the plates facilitated reading of the test. Specific IgM-positive sera showed hemadsorption, whereas negative sera showed hemagglutination. Rheumatoid factor and rubella-specific IgG antibody did not interfere with the results. The test was clearly more sensitive than the solid-phase immunosorbent technique for detection of rubella IgM antibody by hemagglutination inhibition and at least as sensitive as the hemagglutination inhibition test on IgM fractions from a sucrose density gradient and the indirect immunofluorescence test for IgM antibody with absorbed serum. All of 40 sera from 17 rubella patients taken 4 to 49 days after the onset of rash were positive in the new test, with antibody titers ranging from 2,560 to 81,920 between 4 and 28 days. The test is reliable, practical, and suitable for general diagnostic use.     

Hemadsorption immunosorbent technique for the detection of dengue immunoglobulin M antibody.

We developed a highly specific, sensitive, and economical hemadsorption immunosorbent technique for the detection of dengue-specific immunoglobulin M (IgM) antibody. The technique is based on the reaction of human sera with anti-human IgM immobilized onto a solid phase followed by the detection of dengue-specific IgM by the addition of a known quantity of dengue virus hemagglutinin and goose erythrocytes. Dengue-specific IgM-positive sera showed hemadsorption. IgM antibody specific for dengue virus was detected in 22 of 39 (56%) convalescent-phase sera from primary dengue infections and 8 of 10 (80%) convalescent-phase sera from secondary dengue infections. Additionally, 32 of 76 single sera from patients were positive for dengue IgM; these sera were previously uninterpretable by the hemagglutination inhibition test, as only a single serum specimen was available. No false-positive results were obtained with sera that were negative by the hemagglutination inhibition test for dengue virus. Crude dengue virus hemagglutinin preparations could be used without purification. Dengue-specific IgG did not interfere with the results, nor was there any cross-reactivity between dengue hemagglutinins and IgM specific for other viruses. Some cross-reactivity of the dengue-specific IgM was observed with Japanese encephalitis virus hemagglutinins, but this did not present any problems in the interpretation of results. This test is specific, inexpensive, highly reproducible, and simple to perform.     

Enzyme-linked immunosorbent assay for mumps and parainfluenza type 1 immunoglobulin G and immunoglobulin M antibodies

A solid-phase enzyme-linked immunosorbent assay (ELISA) for detection of mumps and parainfluenza type 1 antibodies (immunoglobulin G [IgG] and IgM classes) is described and compared with the conventional complement fixation (CF) test. A highly positive correlation was found between mumps IgG ELISA and the mumps CF test, whereas parainfluenza type 1 IgG ELISA had only a moderate positive correlation with the respective CF test. Mumps IgM antibodies could be demonstrated in all patients with serologically verified and clinically typical (parotitis, meningitis, or orchitis) mumps virus infection, but not in patients with rises in parainfluenza CF titers. Mumps IgM was already present in the acute-phase sera if they were not taken during the first 2 days after onset of disease. Mumps IgM was also found in some paired sera that were taken too late to demonstrate any significant increase in the antibody titers by CF. Therefore, mumps IgM ELISA provides an improvement over the conventional laboratory diagnosis of mumps infection, since the measurement of specific IgM antibodies in a single serum by ELISA is diagnostic, rather than the identification of a fourfold or greater rise in CF antibody titer. An unexpected finding was that parainfluenza type 1 IgM antibodies could not be demonstrated by ELISA in paired sera with rises in parainfluenza CF titers, suggesting a different antibody response from that occurring in mumps infection.     

Direct enzyme-linked immunosorbent assay that uses peroxidase-labeled antigen for determination of immunoglobulin M antibody to cytomegalovirus.

A direct enzyme-linked immunosorbent assay was developed for the measurement of immunoglobulin M (IgM) antibody to cytomegalovirus (CMV). Wells of microtiter plates were coated with anti-human IgM. Each patient's serum was added at a dilution of 1:100, and IgM from the serum was allowed to react with anti-human IgM. The amount of CMV-specific IgM antibody bound was determined by measuring the intensity of color change after the addition of peroxidase-labeled CMV antigen and substrate. Nuclei of infected cells served as an antigen source. CMV IgM could be detected only in IgM fractions of sera from patients with a recent CMV infection. Rheumatoid factor did not cause false-positive results. No cross-reactions were observed when paired sera from 22 patients with herpes simplex or varicella and single sera from 12 patients with suspected infectious mononucleosis were tested by the direct enzyme-linked immunosorbent assay. Each of 17 patients with a seroconversion for CMV antibody showed CMV-specific IgM antibody. In six of these patients the antibody was detected in the initial serum. The direct enzyme-linked immunosorbent assay for CMV IgM is a specific and sensitive test for the diagnosis of recent CMV infections and possesses distinct advantages over indirect tests.     

Enzyme-linked immunosorbent assay for immunoglobulin M specific antibody for the diagnosis of melioidosis.

Indirect hemagglutination (IHA) is commonly used for serodiagnosis of melioidosis. However, in endemic areas, high background titers in normal populations and occasional low titers in patients with septicemic melioidosis prompted a search for a more sensitive and more specific method of serodiagnosis. An indirect fluorescent-antibody test for immunoglobulin M (IgM) specific antibody to Pseudomonas pseudomallei was more sensitive and more specific, but fluorescence microscopes are rarely available in the endemic areas. An enzyme-linked immunosorbent assay (ELISA) for IgM antibody is an attractive alternative. An indirect ELISA for IgM antibody (IgM ELISA) and an IgM antibody capture ELISA for melioidosis were developed. Both tests, together with IHA, were evaluated for 153 serum specimens from blood donors and 16 serum specimens from 16 melioidosis patients. It was found that IHA, the IgM ELISA, and the IgM antibody capture ELISA had sensitivities of 88, 88, and 75%, respectively, with specificities of 97.4, 92.2, and 91.5%, respectively. When IHA was combined with IgM ELISA, a sensitivity of 100% and a specificity of 95.4% were obtained. The IgM ELISA and IHA should be used in combination for serodiagnosis of melioidosis.     

Enzyme-linked immunosorbent assay for detection of immunoglobulin M antibody to hepatitis B core antigen.

An enzyme-linked immunosorbent assay for detection of specific immunoglobulin M (IgM) antibodies against the core antigen of the hepatitis B virus (anti-HBc IgM) is described. The interference of IgM rheumatoid factor was evaluated quantitatively. In the anti-HBc IgM test, the rheumatoid factor gave false-positive results when the concentration exceeded 20 IU/ml. The rheumatoid-positive sera were disclosed by a control and retested for anti-HBc IgM after absorption of rheumatoid factor with latex particles aggregated with human IgG. In five of seven selected patients with acute hepatitis B followed to biochemical and clinical recovery, anti-HBc IgM was present transiently until antibodies against hepatitis B surface antigen (anti-HBs) appeared. Two patients had persistent anti-HBc IgM during the follow-up period. Four patients with hepatitis B surface antigenemia and progression to chronic liver disease did not clear their anti-HBc IgM in the period of observation (11 to 24 months). Anti-HBc IgM could not be demonstrated in 223 of 225 Danish blood donors. The two donors found positive for anti-HBc IgM also had anti-HBs. Twenty patients with acute A or non-A non-B hepatitis were negative for anti-HBc IgM. The enzyme-linked immunosorbent assay for anti-HBc IgM described here has a high specificity and sensitivity. The diagnostic relevance needs further evaluation, including quantitation of anti-HBc IgM, but the results presented indicate that anti-HBc IgM may be helpful in differentiating between prior and recent or ongoing hepatitis B infection.     

Mumps-specific immunoglobulin M and G antibodies in natural mumps infection as measured by enzyme-linked immunosorbent assay

An enzyme-linked immunosorbent assay for the demonstration of mumps immunoglobulin G (IgG ELISA) and immunoglobulin M antibodies (IgM ELISA) in serum was compared with complement fixation (CF), hemagglutination inhibition (HI), and hemolysis-in-gel (HIG) tests. The antibody levels measured by IgG ELISA had a high positive correlation with the CF and HIG tests, whereas only a moderate correlation was found between IgG ELISA and HI. Similar patterns of antibody response were observed with IgG ELISA, CF, and HIG: the antibody titres increased rapidly after the onset of symptoms and reached the maximal values in about three weeks. The HI antibodies developed more slowly during the first week of disease, after which the titres increased rapidly up to the fourth week. IgM antibodies measured by ELISA developed soon after onset of symptoms; most patients had IgM antibodies from the second day, and the highest titres were reached within the first week. The antibody response in mumps parotitis did not differ from that in mumps meningitis/encephalitis, while relatively higher antibody titres were found in patients with orchitis/epididymitis. The diagnostic efficiencies of the methods were compared with serum specimens from 33 patients who had a serologically verified mumps infection by at least one of the five methods used (rising antibody titres in paired sera or detectable IgM): IgM ELISA detected all 33 cases, IgG ELISA 29, HIG 28, HI 23, and CF 13. In 27 cases, IgM antibodies were already present in the acute phase serum specimens. It was concluded that mumps IgM ELISA is a more rapid and sensitive means for the serological diagnosis of mumps infection than the conventional tests.     

Enzyme-linked immunosorbent assay for detection of immunoglobulin M antibody against the Reiter treponeme flagellum in syphilis

An enzyme-linked immunosorbent assay (ELISA) for detection of immunoglobulin M (IgM) antibodies against the periplasmatic flagellum of the Reiter treponeme is described. IgM in the test samples was bound to anti-IgM-coated microtest plates, and flagellum-specific IgM antibody was subsequently detected by incubation with a purified flagellum preparation and monospecific anti-flagellum conjugate. Rheumatoid factor, antinuclear antibodies, or flagellum-specific IgG did not interfere. The specificity of the ELISA for IgM antibodies was 99.5% for sera from 200 blood donors and 98.6% for 147 patient sera that gave false-positive reactions in other syphilis serological tests. The sensitivity was 88.5% for sera from 87 patients with first-time primary syphilis, 93.5% for sera from 62 patients with first-time secondary syphilis, 21.4% for sera from 42 patients who were reinfected, and 0% for sera from 13 patients with late syphilis. Of the sera from 153 patients with treated syphilis, 7.2% had IgM antibodies, and sera from patients with primary or secondary syphilis generally had no IgM antibodies 6 months after treatment. The finding of IgM antibodies indicates that patients should receive antisyphilis treatment if they have not been treated recently, but a negative result does not exclude the possibility of active syphilis. The method may prove useful for the diagnosis of congenital syphilis in newborns.     

Comparison of methods for quantitating antigen-specific immunoglobulin M antibody with a reverse enzyme-linked immunosorbent assay.

We compared two methods for quantitating antigen-specific antibody by a reverse enzyme-linked immunosorbent assay. In the serial-dilution method, the result was determined to be the highest dilution of a serum yielding an absorbance above an established threshold. In the single-dilution method, the result was determined by comparing the absorbance yielded by the test serum at a standard dilution to that yielded by positive and negative reference sera at the same dilution. The results in the single-dilution method reflected the antigen-specific immunoglobulin M antibody activity as a proportion of total immunoglobulin M antibody in a serum, i.e., the immune load, whereas the results in the serial-dilution method reflected the absolute concentration of antigen-specific immunoglobulin M antibody activity. Compared with results in the serial-dilution method, results in the single-dilution method had considerably greater reproducibility on a day-to-day basis and under various test conditions. The single-dilution method was more useful in discriminating between sera from patients in an early stage of clinical infection due to Toxoplasma gondii and sera from patients in a later stage of infection.     

Sensitivity and specificity of viral immunoglobulin M determination by indirect enzyme-linked immunosorbent assay

Four sources of error associated with virus-specific immunoglobulin M (IgM) determination by indirect enzyme-linked immunosorbent assay were recognized and analyzed. First, competitive inhibition due to specific IgG was demonstrated by experiments involving addition and subtraction of rubella-specific IgG. Second, the interference due to rheumatoid factors (RFs) of the IgM class (IgM-RFs) was studied thoroughly, and it appeared that the level of false positivity was more dependent on specific IgG titers than on IgM-RF titers. Third, it was found that some IgM-RFs, differing from conventional IgM-RFs in that they reacted only with isologous IgG, were responsible for further cases of false positivity. Fourth, the interference of an IgM reacting with some virus-unmasked cellular antigens was demonstrated for some uninfected individuals. All four interfering factors could be readily eliminated by simply premixing serum samples with a sheep anti-human gamma-chain serum. This single pretreatment was shown to eliminate false-negatives as well as false-positives in a further 2,004 sera tested for six viruses. These results also emphasize the frequency of RFs and their heterogeneity.     

Enzyme-linked immunosorbent assay for immunoglobulin G antibody to encephalomyocarditis virus

An enzyme-linked immunosorbent assay for immunoglobulin G antibody to encephalomyocarditis virus was developed. This assay was comparable to antibody assay by neutralization. Its adaptability should be useful for laboratory and epidemiological studies of infections due to encephalomyocarditis virus.     

Solid-phase immunosorbent technique for rapid detection of Rift Valley fever virus immunoglobulin M by hemagglutination inhibition.

A solid-phase immunosorbent technique (SPIT) was adapted to detect Rift Valley fever (RVF) virus-specific immunoglobulin M (IgM) in serum samples from humans vaccinated with Formalin-inactivated RVF vaccine. Microdilution plates coated with goat anti-human IgM were successively incubated with serum samples from human vaccinees, RVF virus hemagglutinating antigen, and goose erythrocytes. The RVF virus-specific IgM in the serum samples from vaccinees bound to the RVF virus antigen and inhibited hemagglutination of goose erythrocytes. SPIT was compared to the IgM capture enzyme linked immunosorbent assay (ELISA) and the indirect immunofluorescent-antibody (IFA) assay and was found to be sensitive in detecting RVF virus-specific IgM antibody, with high correlations between SPIT and the other two tests (Pearson's correlation coefficient [r] = 0.9 and 0.6, respectively). Results of SPIT were obtained within 5 h, offering speed over ELISA (8 h). In addition, SPIT does not require sophisticated equipment or expensive reagents. Serum rheumatoid factor did not produce false-positive reactions in SPIT as in the indirect immunofluorescent-antibody assay and IgM capture ELISA.     

Recent vesicular stomatitis virus infection detected by immunoglobulin M antibody capture enzyme-linked immunosorbent assay.

We developed an enzyme-linked immunosorbent assay (ELISA) that was capable of detecting immunoglobulin M (IgM) antibody to vesicular stomatitis virus (VSV) in the sera of experimentally and naturally infected cattle and horses. The detection of IgM in the sera of these animals permitted an estimate of the recency of infection by VSV serotype New Jersey. A VSV serotype New Jersey epizootic strain isolated from a horse and passed once in an Aedes albopictus cell line was used to infect a horse and a calf. Sera from these animals were used to standardize the ELISA. This assay was used to test sera from cattle and horses involved in the 1982 VSV epizootic. Comparative antibody titrations were performed by three systems: the serum-dilution plaque-reduction neutralization, complement fixation, and indirect immunofluorescent tests. The antibody titers by neutralization and the ELISA were comparable for the period that IgM was present; when IgM ELISA titers diminished, the neutralization titers remained high. The complement fixation and indirect immunofluorescent antibody titers followed closely the IgM pattern determined by the ELISA. The capture IgM ELISA is applicable for the rapid detection of IgM antibody to VSV in cattle and horses and is a useful assay of recent infection.     

Enzyme-linked immunosorbent assay for detection ofMycoplasma pneumoniae specific immunoglobulin M

An ELISA was developed for the detection of IgM antibodies to Mycoplasma pneumoniae in human sera, using microtiter plates coated with rabbit antiserum to human IgM selecting for IgM antibodies in the first reaction step. The specific antibodies were detected using enzyme-labelled, detergent-solubilized antigen. The complement fixation test was used as reference method. In a prospective study of 59 patients with community-acquired pneumonia, 13 of whom had evidence of mycoplasmal etiology, the ELISA was shown to have high specificity (97%). In samples taken seven days after onset of the disease all complement-fixation positive samples (n = 20) but one were positive, demonstrating the diagnostic value of a positive test in samples taken after that period.     

Immunoglobulin class and immunoglobulin G subclass enzyme-linked immunosorbent assays compared with microneutralization assay for serodiagnosis of mumps infection and determination of immunity

Total immunoglobulin G (IgG) and IgG subclass reactivities with purified mumps glycoproteins (GP) and nucleoprotein (NP), measured in enzyme-linked immunosorbent assays (ELISAs), were compared with titers in a mumps microneutralization assay (NT). For determination of mumps immunity, the sensitivity of both ELISAs was 100% in comparison with the NT and the specificity was 90%. IgG1 was the dominant subclass against the two antigens found in seropositive healthy individuals. In samples from patients with clinical mumps infections and positive mumps IgM, titer rises of total IgG against NP were invariably seen before GP titer rises. Significant but often late titers rises in NT were found in all patients. Changes of IgG1 levels against both antigens followed the changes of total specific IgG. High levels of IgG3 against NP were diagnostic for mumps infection. In parainfluenza infections, titer rises in the mumps ELISAs and NT were found, but mumps IgM, NP IgG3, and the high ratio between the NP and GP titers found in early samples from patients with mumps infection were not observed.     

Microenzyme-linked immunosorbent assay for detection of immunoglobulin G and immunoglobulin M antibodies to Legionella pneumophila

The microenzyme-linked immunosorbent assay (ELISA) for the detection of immunoglobulin M and G (IgM, IgG) antibodies to Legionella pneumophila serogroup 1 antigens was evaluated. IgM antibodies were measured by both double-sandwich and single-sandwich techniques. These assays were compared with the previously standardized indirect immunofluorescence test in four groups of subjects: (i) pneumonia patients with culture-proven Legionnaires disease with serogroup 1 isolates, (ii) pneumonia patients with serogroup 1 organisms detected by direct immunofluorescence testing of respiratory secretions but without culture confirmation, (iii) pneumonia patients with negative culture and direct immunofluorescence tests, and (iv) healthy hospital employees. In addition, the sensitivity and specificity of the IgG ELISA were evaluated with larger groups of controls and Legionnaires disease patients. The ELISA was more sensitive than the indirect immunofluorescence test. However, it detected antibody rises in pneumonia patients without culture or direct immunofluorescence evidence of L. pneumophila serogroup 1 infection, thereby suggesting that the specificity of the ELISA was slightly lower than that of the indirect immunofluorescence test. The double-sandwich ELISA was a sensitive method for detecting IgM antibodies and, as previously reported, appeared to be free from interference by rheumatoid factor. IgM anti-Legionella antibodies detected by the ELISA appeared earlier and were less persistent than IgG antibodies. In addition, the IgM ELISA was useful in detecting antibodies in necropsy serum samples obtained from patients dying acutely of Legionnaires disease. The data presented show that the ELISA is a reliable method for the detection of specific anti-Legionella antibodies.     

Rapid diagnosis of acute mumps infection by a direct immunoglobulin M antibody capture enzyme immunoassay with labeled antigen

A new immunoglobulin M (IgM) antibody capture enzyme immunoassay with peroxidase-labeled mumps antigen (dMACEIA) is described, and its suitability for practical diagnosis of acute mumps infection is evaluated. All 54 patients with proven mumps infection that were tested showed mumps-specific IgM antibodies. On the other hand, no specific IgM antibodies were present in 16 cases of suspected mumps that could not be confirmed by classical complement fixation serology, and IgM mumps virus antibodies could be detected neither in the sera of 100 healthy individuals nor in those of 16 patients positive for rheumatoid factor. In all, 22 children with acute respiratory illness caused by parainfluenza virus and 44 patients with infections due to other viruses showed no IgM response in mumps dMACEIA. The particular characteristic in which complement fixation antibodies against mumps nucleocapsids appear before and disappear earlier than antibodies to the enveloped mumps virus could not be demonstrated in the dMACEIA. In an extensive epidemic of mumps virus infection, the dMACEIA gave a clear diagnosis of mumps infection in 200 out of 371 suspected cases. By day 2 of the illness, 71% of the patients had detectable IgM, and by day 3, all of them had detectable IgM. In 99% of the cases, dMACEIA gave a positive result in the first available serum specimens, most of which were negative for complement fixation antibodies. A positive but only moderate correlation was thus observed between the two serological procedures. IgM antibodies persisted for at least 6 weeks. The dMACEIA, performed in 3 h, offers a reliable, simple, and rapid alternative to routine methods for detection of acute mumps infection.     

Evaluation of a commercial enzyme-linked immunosorbent assay for detection of immunoglobulin M antibody in diagnosis of human leptospiral infection.

The PanBio Leptospira immunoglobulin M (IgM) enzyme-linked immunosorbent assay (ELISA) is a commercially available screening test for the diagnosis of acute leptospiral infection. The ability of the test to diagnose early or recent Leptospira interrogans infection was assessed by testing sera with known microagglutination test (MAT) titers to serovars pomona, hardjo, copenhageni, and australis. The IgM ELISA detected all 41 cases of early or recent leptospiral infection (sensitivity, 100%), with a positive ELISA result seen in many cases before MAT antibody titers reached 1:50. Thirty-eight of 41 patients showed seroconversion (fourfold or greater increase in titer by MAT, 2 of 41 patients had a single sample with elevated titer, and 1 patient from whom leptospires were isolated from a blood sample failed to show MAT titers, despite a seroconversion (negative to positive result) in the ELISA. Follow-up sera obtained from 8 of 12 patients (67%) for 3 to 48 months after the acute stage of illness showed persisting IgM antibody. However, the range of levels detected in these samples (maximum ELISA ratio, 2.0) was lower than the range seen when infection was recent. Reactivity in the IgM ELISA was observed for only 1 of 59 serum samples from asymptomatic donors (specificity, 98%) and 16 of 233 serum samples from patients with Ross River virus, brucella, Epstein-Barr virus, cytomegalovirus, mycoplasma, Q-fever, toxoplasma, hepatitis A virus, Treponema pallidum, or Borrelia burgdorferi infection (specificity, 93%), with the majority of these patients showing lower levels of IgM in comparison to those in patients with leptospiral infection. We conclude that this ELISA is sufficiently sensitive for use as an initial screen for leptospiral infections, with subsequent confirmation of positive test results by MAT.     

Development and evaluation of a capture enzyme-linked immunosorbent assay for determination of rubella immunoglobulin M using monoclonal antibodies.

A capture enzyme-linked immunosorbent assay (ELISA) for detection of virus-specific immunoglobulin M (IgM) antibody was developed which used a panel of labeled monoclonal antibodies to rubella virus hemagglutinin. The rapidity of the test system was increased by using, after 1-h incubation of the test serum, a second 1-h incubation of the serum with a mixture of viral antigen and labeled monoclonal antibody. The new assay was tested for specificity on 371 human sera from people without any recent contact with rubella virus; of these, 66 were sera selected from people with rheumatoid factor or IgM antibody to human cytomegalovirus, Epstein-Barr virus, or other viruses. In parallel, the new assay was performed on 191 sera from patients having recent contact with rubella virus. Results were compared with those obtained by an indirect ELISA method on IgM serum fractions, using purified rubella virus as a solid phase. Of the 371 sera tested for specificity, 5 (1.3%) gave false-positive results with indirect ELISA (1 rheumatoid factor, 2 heterophil antibody, and 2 human cytomegalovirus sera positive for IgM), and none were false-positive with the capture assay. Two sera from a patient with primary cytomegalovirus infection, which were positive for rubella IgM antibody with both methods and were initially interpreted as false-positive, were finally considered to be true-positive, since they were reactive only in the presence of IgM antibody and viral antigen. Of the 191 sera from 92 patients (84 patients with acute rubella, four newborns from mothers with rubella during pregnancy, and four vaccinees), 136 (71.2%) were found to be positive for IgM by direct ELISA, and 128 (67.0%) were positive by capture ELISA; 12 sera drawn during the first 2 days of disease, or at least 40 days after onset (or after vaccination), were detected only by indirect ELISA, and 4 sera were detected only by capture ELISA. Thus, specificity and sensitivity, respectively, were 100 and 91.4% for capture ELISA and 98.6 and 97.1% for indirect ELISA. However, when the number of patients was considered, 86 were detected as IgM positive by indirect ELISA, and 87 were detected positive by capture ELISA. The overall agreement between the two assays was 96.2%. Capture ELISA using monoclonal antibody appears preferable over indirect ELISA on IgM serum fractions because of its higher specificity and shorter time for test performance; furthermore, there is no need for serum fractionation or virus purification for the capture ELISA.     

Solid-phase enzyme-linked immunosorbent assay for detection of hepatitis A-specific immunoglobulin M.

A solid-phase enzyme linked immunosorbent assay was developed for the detection of immunoglobulin M antibody to hepatitis A virus. The system was capable of detecting hepatitis A-specific immunoglobulin M in a single dilution of serum and appears to be a reliable and rapid means of establishing a diagnosis of hepatitis A infection. Specific immunoglobulin M was only detected in patients with serologically confirmed hepatitis A and not in patients with other forms of hepatitis, chronic liver disease, or autoimmune disease. In patients with hepatitis A, specific immunoglobulin M was usually detectable for 6 weeks after the onset of dark urine, and the longest period for which it was present in any patient was 115 days. This enzyme-linked immunosorbent assay is rapid, simple to perform, and does not require complicated equipment. Provided adequate supplies of purified reagents can be obtained, this enzyme-linked immunosorbent assay procedure is likely to simplify hepatitis A serology, because the same antibody-coated plates can be utilized to detect hepatitis A virus, anti-hepatitis A virus, and hepatitis A-specific immunoglobulin M.