Comparison of enzyme-linked immunosorbent assay (ELISA) and complement fixation test for detection of Mycoplasma pneumoniae antibodies.

An enzyme-linked immunosorbent assay (ELISA) for the detection of IgG and IgM antibodies against Mycoplasma pneumoniae, performed with commercial antigen and reagents, is compared with the complement fixation test (CF) in a serological study of 209 human sera. Concordant results were usually obtained by CF test and by IgG ELISA in sera from patients with recent M pneumoniae infection. In contrast, when used for an immunological survey of a general population, approximately 27% of the sera negative in the CF test were positive for IgG by the ELISA, and sera with low CF titres were found to have a broad range of IgG titre by the ELISA. This may be due to the greater sensitivity of the ELISA technique and/or to different types of antibody measured by both tests. IgM was detected by ELISA in sera from all patients with recent M pneumoniae infection diagnosed on the basis of clinical findings and by CF assay. Occasionally false-positive IgM antibodies were due to rheumatoid factor (RF); this potential interference necessitates routine testing of IgM antibody positive sera for RF.     

Development and evaluation of an enzyme-linked immunosorbent assay (ELISA), using chlamydial group antigen, to detect antibodies, to Chlamydia trachomatis.

Chlamydial group antigen was extracted from Chlamydia trachomatis strain SA2(f) and used as the antigen for an ELISA. The assay was reproducible since chlamydial antibody titres differed by no more than twofold when sera were tested on up to eight occasions. In tests on sera from 75 patients attending venereal disease or rheumatology clinics, the results of the ELISA and of a microimmunofluorescence (MIF) technique were similar for 61 of the sera, that is an 81% agreement. However, the ELISA was a little more sensitive than the MIF technique and at least tenfold more sensitive than the complement fixation procedure. Chlamydial IgG antibody at a titre of 1/greater than or equal to 16 was detected by the ELISA in 6% of children's sera, in 20% of sera from adult patients attending hospital with non-venereal diseases and in 85% of sera from persons attending venereal disease or rheumatology clinics. IgM and IgG antibodies were detected also by the ELISA in the sera of chimpanzees and marmosets which had been infected genitally with C trachomatis and, in general, the titres were greater than those recorded by the MIF test. The value of the ELISA in comparison with the MIF test is discussed.     

Double-conjugate enzyme-linked immunosorbent assay for immunoglobulins G and M against Treponema pallidum

An enzyme-linked immunosorbent assay (ELISA) for the simultaneous measurement of immunoglobulin G (IgG) and IgM was developed to detect antibodies to Treponema pallidum. Wells of polystyrene microtiter plates were coated with T. pallidum antigen, diluted patient serum was added, and IgG and IgM which bound to the T. pallidum antigen were measured by the simultaneous addition of alkaline phosphatase-labeled anti-human IgG and horseradish peroxidase-labeled anti-human IgM. Bound IgG was detected first, followed by bound IgM. After development of the procedure, 145 categorized sera were evaluated: 60 from individuals without syphilis; 62 from patients with syphilis, including 22 with primary, 20 with secondary, and 20 with latent phases of syphilis; and 23 from patients with rheumatoid arthritis. Of the 60 sera from individuals without syphilis, 100% were nonreactive for IgG antibody and 16% were reactive for IgM. Of the 23 sera from patients with rheumatoid arthritis, 3 were reactive for IgG and 3 were nonreactive for IgM. Of the 62 sera from patients with syphilis, 61 (98%) were reactive for IgG antibody with increased titers as the stage of syphilis increased, whereas IgM reactivity decreased. This enzyme-linked immunosorbent assay appears to be a simple method for the simultaneous measurement of antibodies under equal assay conditions.     

Comparative studies of three serologic methods for the measurement of Mycoplasma pneumoniae antibodies

Antibodies against Mycoplasma pneumoniae in the sera of patients and normal adult controls were measured by a standard complement fixation (CF) test, a commercial immunofluorescence (IF) test (CROWNTITRE), and a commercial enzyme-linked immunosorbent assay (ELISA) (MYCOPLASMELISA). The findings showed that, in the control sera, 269 of 277 (97%) had negative results for CF antibodies. Of the 320 controls tested by the IF assay, all (100%) had negative results for IgM antibodies and 314 (98%) had negative results for IgG antibodies. Only 6 of the 201 (3%) controls by the ELISA were classified as negative/equivocal. Among the 450 patient sera, 105 (23%) had positive results for CF antibodies, and 158 (35%) had positive results for IgG and/or IgM membrane antibodies by the IF test; 424 of these patients' sera were also tested by the ELISA, and 397 (94%) of them were found to have positive results for anti-M. pneumoniae IgG antibodies. If the CF test were chosen as the standard for comparison, the IF test would have a sensitivity of 87% and a specificity of 81% and the ELISA would have a sensitivity of 71% and a specificity of 80%, provided an adjustment in the threshold ELISA-positive value was made. A single positive M. pneumoniae membrane IgM antibody titer appeared to be valuable for a presumptive diagnosis of an ongoing infection; 41 of 47 (87%) of the IgM-positive results in the paired sera were supported by a fourfold increase or a stable high level of CF antibody titer.     

Evaluation of Commonly Used Serological Tests for Detection of Coxiella burnetii Antibodies in Well-Defined Acute and Follow-Up Sera

In this study, we compared Coxiella burnetii IgG phase I, IgG phase II, and IgM phase II detection among a commercially available enzyme-linked immunosorbent assay (ELISA) (Virion/Serion), an indirect fluorescent antibody test (IFAT) (Focus Diagnostics), and a complement fixation test (CFT) (Virion/Serion). For this, we used a unique collection of acute- and convalescent-phase sera from 126 patients with acute Q fever diagnosed by positive Coxiella burnetii PCR of blood. We were able to establish a reliable date of onset of disease, since DNA is detectable within 2 weeks after the start of symptoms. In acute samples, at t = 0, IFAT demonstrated IgM phase II antibodies in significantly more sera than did ELISA (31.8% versus 19.7%), although the portion of solitary IgM phase II was equal for IFAT and for ELISA (18.2% and 16.7%, respectively). Twelve months after the diagnosis of acute Q fever, 83.5% and 62.2% of the sera were still positive for IgM phase II with IFAT and ELISA, respectively. At 12 months IFAT IgG phase II showed the slowest decline. Therefore, definitive serological evidence of acute Q fever cannot be based on a single serum sample in areas of epidemicity and should involve measurement of both IgM and IgG antibodies in paired serum. Based on IgG phase II antibody detection in paired samples (at 0 and 3 months) from 62 patients, IFAT confirmed more cases than ELISA and CFT, but the differences were not statically significant (100% for IFAT, 95.2% for ELISA, and 96.8% for CFT). This study demonstrated that the three serological tests are equally effective in diagnosing acute Q fever within 3 months of start of symptoms. In follow-up sera, more IgG antibodies were detected by IFAT than by ELISA or CFT, making IFAT more suitable for prevaccination screening programs.     

Serum IgM Antibodies Contribute to High Levels of Opsonophagocytic Activities in Toddlers Immunized with a Single Dose of the 9-Valent Pneumococcal Conjugate Vaccine

In immunogenicity trials of pneumococcal conjugate vaccines (PCVs), only IgG antibody concentrations to pneumococcal capsular polysaccharides (PPSs) are usually determined, along with the opsonophagocytic activity (OPA) of antipneumococcal antibodies. We aimed to determine the role of both IgG and IgM in OPA in toddlers receiving one dose of 9-valent PCV (PCV9). The IgG and IgM antibody concentrations to PPSs of serotypes 6A, 9V, 14, 19F, and 23F were measured by enzyme immunoassay in sera from toddlers (ages 18 to 35 months) 1 month after a single PCV9 dose. The OPA for the same serotypes was measured by multiplexed opsonophagocytosis assay (MOPA). Further, IgG and IgM concentrations and MOPA were measured to PPS of serotypes 6A, 14, and 19F in sera collected 12 months after vaccination. The detected MOPA titers were high in comparison to the IgG concentrations 1 month after immunization. The IgM concentrations were higher than IgG concentrations for serotypes 6A and 14 (P < 0.001) and as high as IgG for serotypes 9V, 19F, and 23F. Correlation of the IgM antibody concentrations with MOPA (r = 0.35 to 0.65) was stronger compared to that of the IgG antibodies (r = 0.07 to 0.41). The depletion of IgG antibodies in three sets of pooled sera only slightly decreased the OPA activity against serotype 14. At 12 months after immunization, 50 to 100% of serum samples still showed detectable MOPA activity against serotypes 6A, 14, and 19F. Our results suggest that IgM contributes to OPA 1 month after a single PCV9 vaccination in toddlers and that functionally active IgM and IgG antibodies persist for at least a year.     

Immunoglobulin responses to echovirus type 11 by enzyme linked immunosorbent assay: Single-serum diagnosis of acute infection by specific IgM antibody

An indirect solid-phase enzyme-linked immunosorbent assay (ELISA) for the determination of specific IgM and IgG antibodies to echovirus type 11 in a single dilution of serum was developed using partially purified echovirus type 11 bound to microplates. Whole serum was used for IgG antibody but prior to assaying for IgM antibody interfering IgG was removed by ion exchange chromatography. The ELISA for echovirus type 11 IgG antibody was a more sensitive, rapid, technically easier and less costly alternative to the neutralisation test. With the IgG ELISA 12 of 132 sera (10.6%) known to contain enterovirus antibodies other than echovirus type 11 were positive but it could not be determined to what extent this was due to the greater sensitivity of the ELISA or cross-reactions. The IgM ELISA was even more sensitive than the IgG ELISA with acute sera, and showed a reactivity in 4 of 36 sera (11.1%) with no detectable echovirus type 11 neutralising antibodies. Echovirus type 11 IgM antibody was detected in all sera collected after the first week of infection and up to 30 days after infection. However, it was only detected in 58% of sera collected during the first week after onset thus limiting its use for rapid diagnosis. The echovirus type 11 IgM ELISA appears to have considerable laboratory diagnostic potential when a rising antibody level cannot be demonstrated in paired sera or when virus is not cultured.     

Serodiagnosis of Lyme disease by ELISA using Borrelia burgdorferi flagellum antigen

Antibodies to a 41,000 (41 kD) polypeptide in flagella of Borrelia burgdorferi were measured in patients with Lyme disease in Japan by flagellum ELISA. The IgG and IgM Classes of antibodies to a flagellum antigens were detected in the sera as early as 0.5 months after infection. The IgG antibodies continued to exist in their sera for more than one year, while the IgM antibodies quickly faded out from their sera. With respect to a diagnostic specificity of the flagellum ELISA, false positive reactions showing more than 10% were observed in sera with high levels of IgG or IgM, and with anti-syphilis antibody. This method, however, was unaffected by sera with high levels of IgA, rheumatoid factor or anti-nuclear antibody. In three cases of patients with erythema migrans preceded by tick-bite, and treated with antibiotics, seronegative results were observed by a immunoperoxidase (IP) test. Since two of them showed the positive level of IgM antibody by the flagellum ELISA, this method seems to be more sensitive and useful than the IP test for serodiagnosis of the Lyme disease.     

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.     

Counterimmunoelectrophoresis test for immunoglobulin M antibodies to group B coxsackievirus.

A counterimmunoelectrophoresis test was developed for immunoglobulin M (IgM) antibodies to group B coxsackievirus (CB) types 1 through 5. The IgM precipitin line could be identified and differentiated from the IgG line by treating sera with 2-mercaptoethanol. Antigen purity was demonstrated by single precipitin lines occurring only to the homologous antigen when tested with type-specific hyperimmune rabbit sera. Serum pairs from 19 of 22 patients with documented CB type 1,3,4, and 5 infections were positive for IgM antibody to the infecting serotype, whereas 2 of 7 pairs from CB type 2 patients were positive. Heterologous IgM antibodies were present in sera from 14 fo 29 CB patients. Of the 14 patients with heterologous IgM antibodies, 12 also had greater than or equal to 4-fold rises in whole serum neutralizing antibody to heterologous serotypes. Only three control sera from 72 patients with coxsackievirus group A, echovirus, or other viral infections had IgM antibody to CB serotypes.     

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.     

单克隆抗体ELISA间接夹心法检测家鼠型HFRS疫区人和动物血清中特异性抗体

用McAb-ELISA间接夹心法和IFAT或酶标SPA染色法平行检测山西地区(家鼠型HFRS疫区)的人及动物血清中HFRS病毒特异性IgM和/或IgG抗体。结果ELISA检测174份HFRS病人血清的阳性率及抗体滴度均明显高于IFAT。检测295份无明确HFRS病史的健康人血清,ELISA的阳性率也高于IFAT。检测215份鼠类血清,102份兔血清及108份猪血清,ELISA的阳性检出率与IFAT或酶标SPA染色法基本相同。用阻断试验等证明本ELISA检出的确是HFRS病毒特异性抗体。对ELISA的某些试验条件作了讨论,并认为,McAb-ELISA在帮助临床早期诊断及血清流行病学调查等方面均有实用价值。     

Determination of human IgG and IgM class antibodies to West Nile virus by enzyme linked immunosorbent assay (ELISA)

An enzyme-linked immunosorbent assay (ELISA) was developed and used for the detection of IgG and IgM antibodies to West Nile virus in human sera. Thirteen paired sera of clinical cases and 24 control sera taken randomly from a blood bank repository were tested. The sera were reacted in microtiter plates coated with PEG-treated WNV antigen. IgG or IgM antibodies were quantitated by the use of alkaline-phosphatase-conjugated anti-human IgG or IgM antibodies. Of the 24 randomly collected serum samples, 7 were positive in the IgG-ELISA test. One positive by the IgM-ELISA was found to contain rheumatoid factor. In 12 of 13 paired sera of clinical cases, IgM as well as IgG antibodies were detected in the second serum sample taken about 3 wk after the onset of clinical signs. The IgM positive sera were screened for rheumatoid factor (RF) on IgG-coated plates. None of them contained RF. Antibody titers obtained by ELISA showed a good correlation with titers obtained by hemagglutination inhibition, complement fixation, and neutralization tests. The ELISA tests for detection of IgM and IgG antibodies to WNV therefore can replace the other serological methods for epidemiological surveillance and diagnostic purposes.     

A new specific serodiagnosis system for Lyme disease: use of synthetic peptides derived from outer surface protein C of Borrelia burgdorferi

A new specific serodiagnosis system for Lyme disease was developed using the highly specific partial peptide of outer surface protein C of Borrelia burgdorferi. Finally three peptides (OspC-I, -II and -III) were selected from the outer surface protein C (OspC) amino acid sequence of Borrelia burgdorferi sensu lato and were synthesized. OspC-I is located in the region that is conserved among species of Lyme disease spirochetes, whereas OspC-II and -III are located in the variable regions of the OspC from B. garinii type strain 20047. An enzyme-linked immunosorbent assay (ELISA) to detect antibodies against these synthetic peptides was carried out using sera from patients with Lyme disease. Furthermore, sera from patients with syphilis, tsutsugamushi disease and rheumatoid arthritis were used as control sera to demonstrate specificity of each peptide in the ELISA. The results showed that the false positive results in control sera of OspC-I, -II and -III ELISA for immunoglobulin M (IgM) antibody were 8, 22 and 16%, and those for IgG antibody were 11, 43 and 35%, respectively. These results suggested that the ELISA using OspC-I was the most specific. Therefore, sera from patients with Lyme disease were tested OspC-I ELISA. Of the 21 patients, 12 were in the acute phase and nine in the convalescent phase, 17 (81%) were positive by IgM or IgG ELISA. The sensitivities of IgM and IgG ELISA were 83 and 33% for acute-phase sera, and 22 and 78% for convalescent-phase sera, respectively, suggesting that the IgM response to OspC-I peptide was often detectable in the early stage of infection. Our data demonstrated that OspC-I was one of the common epitopes among species of Lyme disease spirochetes, and therefore this is a suitable antigen for serodiagnosis of early stage Lyme disease with high specificity.     

Contribution to laboratory diagnosis of mumps and parainfluenza

Specific IgM and IgG antibodies to mumps virus (MV) were detected in sera of mumps-patients by ELISA in agreement with the results obtained by indirect immunofluorescence (IF). Of given sera 37.5% contained IgM reacting in indirect ELISA also with the antigens of parainfluenza virus (PiV) T3. In all patients with respiratory illness over 2 years of age, the significant increase of antibodies to PiV in haemagglutination inhibition (HI) test was in good correlation with serum IgM and IgG antibody levels to PiV T3 determined by ELISA; but, in addition, 30.7% of these sera cross-reacted with MV antigens. The cross-reactions were eliminated by using MV-nucleocapsid antigen in indirect ELISA, or in direct ELISA using the peroxidase-labelled whole virion antigen. In some children under two years of age a discrepancy was observed between the significant increase of serum antibodies in HI and the inability to detect specific IgM antibodies by means of ELISA in their sera. The low-avidity antibodies appearing after primary PiV infection were probably washed off during the ELISA procedure.     

The interference of IgM rheumatoid factor in enzyme-linked immunosorbent assays of rubella IgM and IgG antibodies

The interference of IgM rheumatoid factor (RF) in the indirect enzyme-linked immunosorbent assay (ELISA) for rubella IgM and IgG antibodies was evaluated quantitatively. In an ELISA for rubella IgM antibodies IgM RF produced false positive results in tests of sera with a rubella IgG concentration exceeding approximately 30 I.U./ml and an IgM RF concentration higher than 3.5 I.U./ml as determined by ELISA. Sera from 3 of 70 patients with recent rubella and sera from a similar proportion of blood donors contained IgM RF in a concentration exceeding this level.The false positive results were reproduced when an IgM RF preparation was added to sera containing rubella IgG. The rubella IgG values in ELISA, however, decreased after the addition of IgM RF . RF was absorbed by incubation of sera with a suspension of latex particles coated with aggregated human IgG. This method prevented the false positive results of the rubella IgM assay and increased the rubella IgM values of rubella convalescent sera. The activity in the rubella IgG assay also increased after absorption of RF. The interference of RF has been explained by a secondary binding of RF to rubella IgG-antigen complexes. The RF might subsequently be detected by the anti-IgM conjugate or compete with the anti-IgG conjugate.The common occurrence of IgM RF in concentrations sufficient to produce false positive results of the ELISA for specific IgM antibodies necessitates routine testing of IgM antibody positive sera for RF by a sensitive method and/or absorption of RF from such sera.     

The enzyme-linked immunosorbent assay (ELISA) for determination of IgG and IgM antibodies after infection with mumps virus

Under routine laboratory conditions ELISA was tested for suitability for serological demonstration of specific antibodies of the immunoglobulin classes G and M against mumps virus. Sera from patients with known clinical and virological data were used. The results of ELISA were compared with those of CFT. 45 paired sera were tested in ELISA IgG, 87 first sera in ELISA IgM. Both tests were highly sensitive, antibodies were detected earlier and with higher titers than with the CFT. The ELISA IgM is particularly suitable for early diagnosis of mumps infection with the first serum. In addition 23 paired sera from patients with acute parainfluenza virus infection were examined for cross-reacting antibodies. Low anti-mumps IgG antibody titers were found in some sera. These findings reduced the mumps specificity of the IgG test. In five serum samples from one patient — obtained before, during, and after an infection with mumps — the course of IgG and IgM antibodies could be demonstrated. Advantages and limitations of ELISA IgG and IgM are summarized.Behringwerke AG, Marburg, West Germany     

Indirect ELISA for the detection of HSV-2 specific IgG and IgM antibodies with glycoprotein G (gG-2).

The glycoprotein G (gG-2) purified from HSV-2 infected cells has been reported to be useful for determination of HSV-2 type-specific antibodies using conventional ELISA formats. This study further confirmed the specificity of gG-2 and demonstrated the feasibility of a specific IgM assay. The gG-2 ELISA was developed to detect HSV-2 specific IgG and IgM antibodies in human sera with high levels of sensitivity and specificity. Of 45 patients with culture-proven recurrent HSV-2 genital infection 44 were reactive for gG-2 IgG. Of 30 sera from patients with culture-proven recent initial HSV-2 genital infection 29 were positive for gG-2 IgM. Three patients with primary HSV-2 genital infection showed gG-2 IgM in the convalescent but not in the acute sera. The IgG- and IgM-gG-2 ELISA showed high specificity. None of 40 sera from children were reactive by either assay. Only one of 94 sera from patients with antibody to herpesviruses other than HSV reacted in the IgG assay but none reacted in the IgM assay. There was no cross-reaction with sera from patients with proven HSV-1 infection with the gG-2 antigen. The results suggest that the IgG assay can be used for demonstration of past HSV-2 infection and the IgM assay for the diagnosis of HSV-2 in neonatal herpes and primary genital herpes, when cultures or rapid diagnostic techniques are unavailable.     

Serodiagnosis of smear and culture-negative neurotuberculosis with enzyme linked immunosorbent assay for anti A-60 immunoglobulins

Early diagnosis of neurotuberculosis (NTB), useful in prevention of mortality and morbidity, remains a challenge despite availability of several tests. An ELISA test to detect IgG and IgM antibodies against Mycobacterial antigen A-60 (Anda Biologicals, France) was done in 677 specimens; group 1 (NTB): 373 sera and 167 cerebrospinal fluid (CSF), group 2: 100 sera from healthy subjects, group 3: 17 CSF from patients undergoing neurosurgical operations for non-tubercular diseases. Anti-A 60 IgA estimation was done in 99 sera from group 1 and all 100 from group 2. Working dilutions were 1:200 for serum and 1:10 for CSF. Serum IgM and IgG anti-A 60 antibodies were more often detected in group 1 than in 2 (50% Vs 10%, p<.001). Anti-IgG and IgM antibody were detected more often in group 1 than in group 3 (33% Vs 6%, p<.001). In serum and CSF both IgM positivity was more than IgG in 2 subgroups of NTB and these are tubercular meningitis, spinal tuberculosis whereas in tuberculoma IgG positivity was more as compared to other 2 groups. Sera were more often positive than CSF (50% Vs 33%, p<.001). Of 32 patients, in whom magnetic resonance imaging (MRI) was done, 15/18 (83%) patients with suggestive findings in MRI had a positive ELISA (IgG or IgM). AntiA-60 antibody is a useful aid in the diagnosis of NTB, especially in smear and culture negative NTB where one does not have much diagnostic opportunities to choose from.