Detection of antibodies against Trypanosoma cruzi in Somoto, Nicaragua, using indirect ELISA and IFI on blood samples on filter paper]

We standardized a solid-phase enzyme-linked immunosorbent assay (ELISA) in order to study the presence of Trypanosoma cruzi antibodies in asymptomatic persons who live in an area of Nicaragua endemic for Chagas' disease. The test was standardized to analyze filter-paper blood samples, which are easy to transport. In the first phase of our investigation, ELISA was used to study 18 samples of total serum and 18 eluates of blood from patients with chronic Chagas' disease; 30 samples of serum and 30 eluates of blood from healthy people, used as negative controls; and 14 samples of serum and 14 eluates of blood from patients with cutaneous or visceral leishmaniasis, which were used to study cross-reactions. Both with the total-serum and the blood-eluate samples, the ELISA test provided 100% sensitivity and 90% specificity. Cross-reactions in the patient samples were observed only with visceral leishmaniasis. The second phase of our investigation was a population study that included eight rural communities in the area of Somoto, Nicaragua. Through random sampling, filter-paper blood samples were collected from 2,434 people (1,335 men and 1,099 women) from the communities of Aguas Calientes, El Brocal, La Manzana, Las Playas, Los Canales, Santa Isabel, Santa Rosa, and Santa Teresa. Studied by ELISA and by indirect immunofluorescence (IIF), the samples included 260 found seropositive by ELISA (10.7%), of which 207 were positive according to IIF (8.5%). With both techniques, the majority of seropositives were among women, but the difference between men and women was not statistically significant. There was a high level of agreement between the results obtained with the two techniques. There was an upward trend with age, with 5.4% of those found seropositive by ELISA being persons 10 years of age or younger and 42.7% of those found seropositive being older than 50. The vast majority of the individuals analyzed were asymptomatic.     

The serological diagnosis of Mycoplasma pneumoniae infection: a comparison of complement fixation, haemagglutination and immunofluorescence

A total of 193 sera were examined for antibody to Mycoplasma pneumoniae by three techniques - complement fixation (CF), haemagglutination (HA) and immunofluorescence (IF), the last method being used to assess IgM, IgG and IgA antibodies. The most reliable single test for diagnosis was HA, and the most useful combination of tests was HA with IF (IgM and IgG). The IgA IF was not found to be diagnostically helpful.     

The serological diagnosis of Mycoplasma pneumoniae infection: a comparison of complement fixation, haemagglutination and immunofluorescence.

A total of 193 sera were examined for antibody to Mycoplasma pneumoniae by three techniques - complement fixation (CF), haemagglutination (HA) and immunofluorescence (IF), the last method being used to assess IgM, IgG and IgA antibodies. The most reliable single test for diagnosis was HA, and the most useful combination of tests was HA with IF (IgM and IgG). The IgA IF was not found to be diagnostically helpful.     

Inter-test reliability of the anti-RESA indices based on ELISA tests using eluates from whole blood spots dried on filter paper

The ring-infected erythrocyte surface antigen (RESA), is one of the falciparum malaria vaccine candidates rarely studied in Brazil. Fieldwork logistics to conduct serology studies is simplified when eluates from whole blood dried on filter paper can be used. Therefore, this study aimed to assess the inter-test reliability for the anti-RESA ELISA-based indices using eluates from filter paper and from serum samples. The study population consisted of 210 individuals (Brazil) from whom matched samples were collected. Anti-RESA ELISA-based index means (+/- S.D.) were 15.29% (+/-28.13%) for filter paper and 11.79% (+/-23.67%) for serum samples. The intra-class correlation coefficient was estimated to be 82.38%, indicating high test reliability. However, there was a significant tendency for filter paper test results to have higher values than serum sample test results (P < 0.001). Explanations for this finding may be the presence of haemoglobin in the eluates from filter paper, which may interfere with ELISA testing.     

Detection of antibodies against hepatitis A virus in eluates of blood spotted on filter-paper: a pilot study in Rio de Janeiro, Brazil

The validity of blood spotted on to filter-paper (BSOFP) eluates for the detection of antibodies against hepatitis A virus (HAV) was investigated in 718 individuals (children and adults) during a field study in a small area in Rio de Janeiro State, Brazil. Serum samples were considered the 'gold standard'. BSOFP eluates were analyzed by 2 different techniques: microplate competitive enzyme-linked immunosorbent assay (ELISA) of the whole study group and microparticle enzyme immune assay (MEIA) of a subsample of 59 individuals. For BSOFP eluates by ELISA, sensitivity and specificity were 89.6% (95% CI: 84.7-93.1) and 97.5% (95% CI: 95.6-98.7), respectively. For a seroprevalence of anti-HAV antibodies of 32%, the positive predictive value was 94.5% (95% CI: 90.3-97.0) and the negative predictive value was 95.2% (95% CI: 92.8-96.8). The test efficiency was 95.0% (95% CI: 93.1-96.4). Similar results were found for BSOFP eluates by MEIA. Agreement between the 2 techniques used for BSOFP (ELISA and MEIA) was also high (kappa = 0.93). These results encourage the more widespread application of BSOFP as a means of surveillance for large-scale epidemiological studies for hepatitis A.     

Diagnostic performance indices for immunofluorescent tests and enzyme immunoassays of leishmaniasis sera from northern and north-eastern Brazil

A total of 341 sera were screened for anti-Leishmania IgA, IgG, and IgM antibodies by immunofluorescent (IF) tests and enzyme immunoassay (ELISA). Altogether, 292 of the sera originated from patients with clinically as well as parasitologically diagnosed (positive lesion imprint or the Montenegro skin test) cutaneous leishmaniasis; 49 of the sera were from controls from the same base population. In terms of diagnostic performance, the ELISAs for IgG and IgM yielded indices of diagnostic utility, and the positive predictive value for the IgG-ELISA was 94.6%. A remarkably high specificity (100%) was obtained with the IgA-IF test, but its sensitivity was very low.     

Incidence of hepatitis C virus antibodies in blood donors, high risk patient groups, liver diseases and health professionals. Multicenter study of the ABBOT ELISA method, comparison with the ORTHO test

Serum samples from 1185 individuals (blood donors, health care workers, patients on haemodialysis or from other high risk groups or with non-A, non-B [NANB] hepatitis and other liver diseases) were examined for antibody to a recombinant antigen of hepatitis c virus (anti-HCV). A new ABBOTT HCV EIA system was used and a parallel study with ORTHO HCV ELISA was also done for 380 samples to compare the two anti-HCV tests. A confirmatory neutralizing ABBOTT ELISA probe was also performed in 45 cases. Anti-HCV seropositivity was found in 1.60% of accepted healthy blood donors, while among subjects excluded from donation for elevated aminotransferase the rate was 8.95%. In patients on haemodialysis 47.15% anti-HCV prevalence was found, in other high risk group subjects 32.5%. Patients with acute post-transfusion (PT) NANB hepatitis showed 40% prevalence, this rate in chronic PT-NANB was 77.8%. The two ELISA tests revealed 95% agreement in the parallel determinations. Serial dilution studies of anti-HCV positive sera showed that ABBOTT test was of superior sensitivity. The results of the confirmatory test suggest that reactive (positive) samples of low optical density near to the cut-off value require a confirmation with the neutralization test. In conclusion HCV infection in Hungary seems to be a common aetiologic factor in PT-NANB hepatitis and the screening of blood donors for anti-HCV may be useful. However, because of financial difficulties, cost/benefit calculations are recommended before the introduction of this preventive measure.     

Evaluation of serological diagnostic indices for mucocutaneous leishmaniasis: immunofluorescence tests and enzyme-linked immunoassays for IgG, IgM and IgA antibodies

The sensitivity, specificity, positive predictive value, negative predictive value, and efficiency of immunofluorescence (IF) and enzyme-linked immunoassays (ELISA) for IgG, IgM and IgA antibodies were assessed on sera from mucocutaneous leishmaniasis patients and controls. The sensitivity of the IgG-ELISA test was 93.3% with 95% confidence interval higher than what could be due to a random test not associated with the disease. The specificity of all tests, except the IgM-ELISA, gave indices that could not have been due to chance. The IgG-ELISA and IgG-IF had the highest positive predictive value and the kappa statistic showed that the strength of agreement between the disease and the test was strongest for IgG-ELISA. The IgG-ELISA had a negative predictive value with 95% confidence limits that were not due to chance alone. Efficiency was highest for IgG-ELISA and IgG-IF. These results were obtained using sera from patients with severe or long-standing disease and from controls in whom the disease was ruled out by a negative Montenegro skin test. In field surveys where the differences between cases and controls are less easy to define the diagnostic indices of these tests may vary with the disease prevalence.     

External evaluation of serology results in blood banks in Colombia]

OBJECTIVE: To analyze the serological results found in Colombian blood banks that participate in the external quality program (EQP) of that country's National Institute of Health, in order to improve the quality of the screening of blood for the main serological markers of transfusion-transmitted infectious diseases. METHODS: Each blood bank received a panel of six sera with different reactivity and positivity to hepatitis B surface antigen (HBsAg), as well as to antibodies to HIV 1-2, Trypanosoma cruzi (the causative agent of Chagas' disease), Treponema pallidum (the causative agent of syphilis), hepatitis B core (HBc) antigen, hepatitis C virus (HCV), and human T-lymphotropic virus (HTLV). The screening techniques used were enzyme-linked immunosorbent assay (ELISA), microparticle enzyme immunoassay (MEIA), and hemagglutination. With the panel sera, the participating blood banks were asked to apply the same tests that they use on a daily basis to screen blood units and to send their results to the National Blood Banks Unit of the Colombian National Institute of Health. RESULTS: Of the 46 blood banks participating in the EQP, 43 of them (93%) returned their results within the requested timeframe. The ELISA test was the one that was used most often (83.0%). There were a total of 49 (5%) false positive results and 12 (3%) false negative results. Of those 12 false negative results, 6 of them corresponded to the detection of syphilis, 2 to Chagas' disease, 2 to anti-HBc antibodies, 1 to anti-HCV antibodies, and 1 to HBsAg. Eighty percent of the discordant results came from 23 blood banks that each collected fewer than 6 000 units of blood per year, and 15% came from 5 blood banks that collected 6 000 to 12 000 units per year. One of the blood banks that collected more than 12 000 units annually had three false positive results, and none of those larger blood banks had any false positive results. CONCLUSIONS: The percentage of false negative results (3%) found during the EQP can be considered high, since tests that are negative during blood screening are not repeated, and the decision to declare a unit of blood suitable for transfusion is based on that single result. There is a need to thoroughly review the procedures for screening blood in Colombia, particularly at the centers that performed poorly in this EQP exercise.     

Evaluation of antigen detection and antibody detection tests for Trypanosoma evansi infections of buffaloes in Indonesia.

Two Ag-ELISAs, an IgG-specific antibody detection ELISA (IgG ELISA) and a card agglutination test (CATT) for the detection of Trypanasoma evansi infections in buffaloes in Indonesia, were compared. Diagnostic sensitivity estimates were obtained by testing sera from 139 Indonesian buffaloes which had been found to be infected by parasitological tests. Diagnostic specificity was estimated by testing sera from 263 buffaloes living in Australia. Response-operating characteristic curves were constructed, and optimal ELISA cut-off values, which minimized the number of false-negative and false-positive results, were chosen. The IgG ELISA had the highest sensitivity (89%) and the CATT had the highest specificity (100%). There was a significant difference between the sensitivities (71 and 81%), but not between the specificities (75 and 78%), of the two Ag-ELISAs. The four tests were further compared by calculation of post-test probabilities of infection for positive and negative test results using a range of prevalence values, and likelihood ratios. The results suggested that the CATT was the best test to 'rule-in' infection (i.e. the highest probability of infection in test-positive animals) and the IgG ELISA was the best test to 'rule-out' infection (i.e. the lowest probability of infection in test-negative animals).     

Evaluation of Lepto Dri Dot as a rapid test for the diagnosis of leptospirosis

Lepto Dri Dot is a new card agglutination test developed by the Dutch Royal Tropical Institute for the rapid diagnosis of leptospirosis. We evaluated the test in field conditions in The Andaman Islands. Patients suspected of leptospirosis who attended three primary health centres were included in the study. The test results were compared with blood culture or microscopic agglutination tests on paired serum samples; 74 of 124 patients were diagnosed as having leptospirosis based on these criteria. Lepto Dri Dot had a sensitivity of 67.6% (50/74) and a specificity of 66.0% (33/50) during week 1. During weeks 2-4 the values increased to 85.5% (47/55) and 80% (40/50) respectively. An IgM ELISA was also performed on the serum samples for comparison and this was marginally less sensitive, but more specific, during the first week of illness. The positivity rates for the Dri Dot test during days 2-3, 4-5 and 6-7 were 53.1% (17/32), 75.0% (18/24) and 83.3% (15/18), respectively. The corresponding values for ELISA were 28.1% (9/32), 54% (13/24) and 77.8% (14/18). Both Dri Dot and ELISA showed good agreement with the standard diagnostic criteria after the first week of illness (kappa= 0.65 and 0.74, respectively). The overall concordance of the two tests was 89.5 % (kappa = 0.79). The test does not require special storage or sophisticated equipment and can be performed by relatively low skilled personnel.     

Serological diagnosis of human immuno-deficiency virus in Burkina Faso: reliable, practical strategies using less expensive commercial test kits.

Reported are the results of a cross-sectional survey in Burkina Faso to identify reliable, practical strategies for the serological diagnosis of HIV-1 and/or HIV-2 infections, using less-expensive commercial test kits in various combinations, as an alternative to the conventional Western blot (WB) test, which costs US$ 60. Serum samples, collected from blood donors, patients with acquired immunodeficiency syndrome (AIDS) and pregnant women, were tested between December 1995 and January 1997. Twelve commercial test kits were available: five Mixt enzyme-linked immunosorbent assays (ELISA), three Mixt rapid tests, and four additional tests including monospecific HIV-1 and HIV-2 ELISA. The reference strategy utilized a combination of one ELISA or one rapid test with WB, and was conducted following WHO criteria. A total of 768 serum samples were tested; 35 were indeterminate and excluded from the analysis. Seroprevalence of HIV in the remaining 733 sera was found to be 37.5% (95% confidence interval: 34.0-41.1). All the ELISA tests showed 100% sensitivity, but their specificities ranged from 81.4% to 100%. GLA (Genelavia Mixt) had the highest positive delta value, while ICE HIV-1.0.2 (ICE) produced the most distinct negative results. Among the rapid tests, COM (CombAIDS-RS) achieved 100% sensitivity and SPO (HIV Spot) 100% specificity. Various combinations of commercial tests, according to recommended WHO strategies I, II, III, gave excellent results when ICE was included in the sequence. The best combination of tests for strategy II, which achieved 100% sensitivity and specificity, was to use ICE and COM, the cost of which was US$ 2.10, compared with US$ 55.60 for the corresponding conventional strategy. For strategy III, the best combination, which achieved 100% sensitivity and specificity, was to use ICE, ZYG (Enzygnost Anti HIV-1/HIV-2 Plus) and COM, the cost of which was US$ 2.90 (19.2 times lower than the corresponding strategy requiring WB). No rapid test combination showed 100% sensitivity and specificity. Our results indicate that the serodiagnosis of HIV in Burkina Faso is possible by using reliable, less-expensive strategies which do not require Western blot testing. Moreover, there is a choice of strategies for laboratories working with or without an ELISA chain.     

A comparative study of serological techniques for detection of West Nile virus antibodies

This study was conducted to compare different serological techniques namely enzyme-linked immunosorbent assay (ELISA), hemagglutination inhibition (HI), indirect immunofluorescence (IFT) and plaque reduction neutralization (PRNT), for detection of West Nile virus (WNV) antibodies in sera collected from inhabitants of a flooded village (Begiram, Minufiya Governorate). ELISA showed 45% while HI and IFT indicated 37.6 and 26.4% positive sera among the tested 178 sera taken from the flooded village, respectively. The results obtained by ELISA, HI and IFT of only 55 randomly chosen sera were compared with their PRNT results. ELISA was found to be more sensitive (83.8%) while IFT and HI were more specific (88.9% and 83.3%, respectively). The positive predictive values for the 3 tests were more than 80% while the negative predictive values were different for these tests: 66.7% for ELISA, 44.1% and 37% for HI and IFT, respectively. From this study it is concluded that for screening of population in an endemic area, two serological tests in combination can be used starting with ELISA (the more sensitive) followed by HI and/or IFT (the more specific) to exclude the false positive results.     

Seroprevalence of anti-hepatitis C virus antibodies among blood donors,Brazil

OBJECTIVE: To determine the seroprevalence of anti-hepatitis C virus antibodies (anti-HCV) in blood donors, and to describe the correlation between screening serological test results and confirmatory test. METHODS: Epidemiological and laboratorial records of 10,090 blood donors of the blood unit in the city of Apucarana, Brazil, from January 1997 to December 1999 were assessed. Anti-HCV serum antibodies were detected using enzyme-linked immunosorbent assay (ELISA). Serum reactive samples were tested using RIBA (recombinant immunoblot assay). Statistical analysis was performed using Chi-square test, Fischer's test and Kappa index of agreement. RESULTS: The results showed that of all the donors, 2,461 (24.4%) were females, 7,629 (75.6%) were males, with ages ranging from 18 to 65 years old. Of 10,090 serum samples tested using ELISA, 88 were reactive to anti-HCV, a seroprevalence of 0.9% that showed no association with either age groups (p=0.197) or sex (p=0.323). When the samples were tested using RIBA, 11 (12.5%) were positive, 14 (15.9%) were indeterminate, and 38 (43.2%) were negative. Statistical analysis revealed a high correlation (kappa index 0.939) between ELISA and RIBA test results. Poorly reactive samples in ELISA showed a high correlation with negative results in RIBA, and samples highly reactive in ELISA showed a high correlation with positive results in RIBA. CONCLUSIONS: The results stress the need of confirmatory tests for all anti-HCV reactive samples in screening tests. HVC infection confirmation is paramount for clinical, laboratorial, and histological evaluation of blood donors.     

IgM抗体捕捉ELISA法在麻疹血清学诊断上的优越性

本文用ACELISA法、ELISA-IgG法、HI法测定了临床诊断为麻疹的100对患者双份血清,其中8份三种方法都为阴性。余92对血清的三种方法诊断阳性率分别为ACELISA法98.9%,ELISA-IgG法82.6%,HI法69.4%,证明ACELISA法是诊断麻疹较好的方法,有敏感、特异、早期、多数仅需单份血清就能诊断等的优点。IgM抗体发病第二天开始出现,病后第2周达到高峰,一个月后明显下降或阴转,故ACELISA法诊断的适宜采血时期为发病第3~25天。     

Evaluation of a synthetic tripeptide as antigen for detection of IgM and IgG antibodies to Trypanosoma cruzi in serum samples from patients with Chagas disease or viral diseases

An enzyme-linked immunosorbent assay (ELISA) has been developed to detect IgG and IgM antibodies in human sera against a synthetic tripeptide derived from a hybrid peptide containing 3 specific epitopes from Trypanosoma cruzi. This assay was compared in Brazil with one using conventional antigen, the alkaline crude extract. Serum samples were divided into positive (40 samples) or negative (107 samples) for Chagas disease. Positive samples included 9 serum samples from patients with acute Chagas disease, while negative samples included 57 samples from patients suffering from viral diseases. The total percentages of IgG positive samples from patients with chronic Chagas disease for alkaline extract and synthetic tripeptide were 93.5% and 100%, respectively. All samples from patients with acute Chagas disease were confirmed positive for IgM antibodies by using both the tripeptide and the alkaline extract. However, the results for anti-T. cruzi IgM in the group of chronic Chagas disease patients demonstrated that 41.9% were positive for IgM with the alkaline extract, while the synthetic peptide showed a significantly lower number of positive samples (12.9%). The serum samples from healthy people showed similar results for both antigens. However, 40% of the serum samples from patients presenting with viral diseases were IgM positive for Chagas disease when assayed with conventional antigen; with the synthetic tripeptide as antigen, 100% of this group of samples were found to be negative. Thus, as the results of ELISA with synthetic tripeptide showed higher rates of sensitivity and specificity than ELISA with conventional antigen, the former should be included as a laboratory tool in the serodiagnosis of Chagas disease.     

Field evaluation of the use of an ELISA to detect chloroquine and its metabolites in blood, urine and breast-milk

The evaluation of an enzyme-linked immunosorbent assay (ELISA) for chloroquine and its metabolites in blood, urine and breast-milk is reported. ELISA blood levels, following standard treatment with chloroquine of pregnant and non-pregnant women, showed mean values comparable to other analytical methods. Blood chloroquine concentrations were estimated at day 0, 350-400 ng/ml; day 2, 1000-1500 ng/ml; day 14, 350-400 ng/ml; day 28, 180-350 ng/ml. In a separate sample a significant association was observed between history of chloroquine use in the previous 2 weeks and blood ELISA values (P less than 0.01). Mean ELISA values in breast-milk were higher than in corresponding whole blood samples. High concentrations of chloroquine in urine were observed. There was a weak association of the ELISA of urine and blood samples collected at the same time (P = 0.076). This study confirms the low sensitivity (less than 55%) of the Dill-Glazko test in urine, which is 100-1000 times less sensitive than the ELISA; the latter can detect 10-20 ng chloroquine per ml. A cut-off value for blood positivity 2 weeks following therapeutic drug ingestion was determined (40% ELISA inhibition), which can be used to make decisions about subject selection in drug sensitivity tests or population surveys. There are several advantages with the ELISA under field conditions. These include direct measurement of whole blood concentration; avoidance of problems of urine collection; suitability of finger-prick samples, especially with young children; application to population surveys to monitor drug use; and selection of subjects for drug sensitivity tests and monitoring of blood levels during in vivo tests.     

A survey of coxsackie A16 virus antibodies in human sera.

A comparison of neutralizing and immunofluorescent (IF) IgG antibody tests in 18 sera from 10 cases of hand, foot and mouth disease (HFMD) showed a variety of responses but all sera taken more than one week after infection had both neutralizing and IF IgG antibodies. A survey of IF IgG antibody in 80 paediatric and 80 adult non-HFMD case sera gave antibody detection rates of 47.5% and 11.3% respectively. This difference could be attributed to a decline in IF IgG antibody with time after infection. Three point nine per cent of 26 sera from possible adult carditis cases had IF antibody suggesting that coxsackie A16 virus was not a common cause of adult carditis. Forty-eight point three per cent of 29 sera from cases of spontaneous abortion had detectable IF antibody, a rate similar to the paediatric sera and significantly greater than that in adult male (7.9%) and other adult female (13%) sera tested. This interesting observation requires further study.     

A survey of coxsackie A16 virus antibodies in human sera

A comparison of neutralizing and immunofluorescent (IF) IgG antibody tests in 18 sera from 10 cases of hand, foot and mouth disease (HFMD) showed a variety of responses but all sera taken more than one week after infection had both neutralizing and IF IgG antibodies. A survey of IF IgG antibody in 80 paediatric and 80 adult non-HFMD case sera gave antibody detection rates of 47.5% and 11.3% respectively. This difference could be attributed to a decline in IF IgG antibody with time after infection. Three point nine per cent of 26 sera from possible adult carditis cases had IF antibody suggesting that coxsackie A16 virus was not a common cause of adult carditis. Forty-eight point three per cent of 29 sera from cases of spontaneous abortion had detectable IF antibody, a rate similar to the paediatric sera and significantly greater than that in adult male (7.9%) and other adult female (13%) sera tested. This interesting observation requires further study.     

Diagnosis of tuberculous meningitis by immunofluorescence and enzyme immunoassay

Cerebrospinal fluid was collected from 29 patients with tuberculous meningitis, 21 and 7 patients with bacterial and viral meningitis and 5 normal subjects. Pressure, aspect, glucose, protein and cellular content of CSF were studied. Detection of acid fast bacilli in direct film stained by Zeil Neilsen (Z.N.) and fluorochrom (Fl.Ch.) and Culture on Lowenstein Jensen media were done. Then specific immunoglobulin G & M to Mycobacteria were assayed by Immunofluorescence (IF using BCG) and by Enzyme Linked Immunosorbant assay (ELISA) using protein-A of M. Tuberculosis. It was found that diagnosis of M. Tuberculosis by CSF culture was more sensitive than by direct CSF film stained with Z.N. or Fl.Ch. stain (positive in 44.8%, 10.3% and 17.2% of cases respectively). It was noticed that the detection of CSF IgG antibodies was more sensitive than IgM antibodies either by IF or ELISA. By comparing ELISA and IF tests for detection of specific anti-mycobacterial immunoglobulin in CSF, it was clear that the sensitivity and specificity of ELISA was more than IF test. A positive result for antimycobacteria IgG antibodies was obtained in 79.3% and 58.6% of cases respectively (p less than 0.05). None of the CSF of normal controls, bacterial and viral meningitis cases gave positive antimycobacteria IgG by ELISA while 9.5% of the CSF of bacterial and 14.3% of aseptic meningitis cases gave positive results with IF. The sensitivity, specificity and predictive value of the described ELISA test, make it useful for early diagnosis of tuberculous meningitis.