Significance of serum galactose deficient IgA1 as a potential biomarker for IgA nephropathy: A case control study.

BACKGROUND: IgA nephropathy(IgAN) is a common glomerular disease with a higher risk of progression to end stage renal disease (ESRD) in certain ethnic populations. Since galactose deficient IgA1(Gd-IgA1) is a critical molecule in its pathogenesis, it has generated interest as a biomarker for this disease. METHODS: We measured serum Gd-IgA1 levels using a non- lectin based enzyme linked immunoassay(ELISA) in 136 immunosuppression naïve patients with primary IgAN and 110 controls(60-non IgA glomerular diseases, 50-healthy volunteers). RESULTS: Median serum Gd-IgA1 levels were significantly higher in IgAN patients [13135.6(2723.3,59603.8)ng/ml] compared to those with non IgA glomerular disease [4954.8(892.9,18256.2) ng/ml] and healthy controls [6299.5(1993.2,19256) ng/ml] and this was observed even after log transformation and adjustment for age and gender(p<0.0001). Considering a cut-off value of serum Gd-IGA1≥7982.1ng/ml, the sensitivity for diagnosing IgAN compared to healthy controls was 74.3% and specificity was 72.0% with a positive predictive value of 87.8% and negative predictive value of 50.7%. The serum Gd-IgA1 level did not co-relate with baseline estimated glomerular filtration rate, urine protein creatinine ratio and the M, E, S, T and C scores on renal biopsy. The renal survival (absence of >30% decrease in eGFR, ESRD or death) was lower in patients with higher serum Gd-IgA1 levels(≥7982ng/ml) than those who had lower levels but it was not statistically significant(p = 0.486). CONCLUSION: Serum Gd-IgA1 level is higher in IgAN patients compared to non-IgA glomerular diseases and healthy controls and has a good positive predictive value for diagnosis. However, it does not correlate with clinical and histological characteristics of disease severity and does not predict disease progression.

Comparison of Xpert MTB/RIF with line probe assay for detection of rifampin-monoresistant Mycobacterium tuberculosis.

The MTBDRplus line probe assay (LPA) and Xpert MTB/RIF have been endorsed by the World Health Organization for the rapid diagnosis of drug-resistant tuberculosis. However, there is no clarity regarding the superiority of one over the other. In a double-blinded prospective study, we evaluated the efficacy of the Xpert MTB/RIF on samples that were first tested by LPA under the revised national tuberculosis control program of India. A total of 405 sputum samples from suspected drug-resistant tuberculosis patients were included. Of these, 285 smear-positive samples were subjected to LPA. Seventy-two (25.8%) samples showed multidrug resistance, 62 (22.2%) showed rifampin monoresistance, 29 (10.3%) showed isoniazid monoresistance, and 116 (41.5%) were pan-susceptible. Six (2.1%) of the samples gave invalid results. Of the 62 rifampin-monoresistant samples by LPA, 38 (61.4%) showed rifampin resistance, while 21 (33.8%) were found susceptible to rifampin by Xpert MTB/RIF using cartridge version G4. Three (4.8%) samples gave an error. Of the 116 pan-susceptible samples, only 83 were available for Xpert MTB/RIF testing; 4 (5.1%) were rifampin resistant, 74 (94.8%) were susceptible, and 5 (6.0%) showed an error. The 25 discrepant samples were further subjected to MGIT960 drug susceptibility testing. The MGIT960 results showed 100% agreement with LPA results but only 64.4% agreement with Xpert MTB/RIF results. Sequencing analysis of discrepant samples showed 91.3% concordance with LPA but only 8.7% concordance with the Xpert MTB/RIF assay. These findings indicate that by using Xpert MTB/RIF testing we might be underestimating the burden of drug-resistant tuberculosis and indicate that country-specific probes need to be designed to increase the sensitivity of the Xpert MTB/RIF.

High degree of multi-drug resistance and hetero-resistance in pulmonary TB patients from Punjab state of India.

Line Probe Assays (LPAs) have been recommended for rapid screening of MDR-TB. Aims of this study were (1) to compare the performance of LPA with standard Bactec MGIT 960 system and (2) to ascertain the pattern of genetic mutations in the resistance isolates. In phase I, a total of 141 Mycobacterium tuberculosis isolates from our routine laboratory were tested by LPA and Bactec MGIT 960 for DST. In phase II, 578 sputum specimens of suspected DR-TB patients were received from the Punjab state of India. Of them 438 specimens or their cultures were subjected to LPA. The presence of mutant bands with their corresponding wild type band was identified as "hetero-resistance". In phase I, LPA showed high concordance with 96.4% positive agreement and 97.6% negative agreement with Bactec MGIT 960-DST. In phase II, 12 (2.7%) specimens were detected as invalid by LPA. Of the remaining 426 specimens, 184 (43.1%) had resistance to RIF and 142 (33.3%) to INH while 103 (24.1%) specimens showed resistance to both INH and RIF (MDR-TB) by LPA. Of the 142 INH resistant, 113 (79.5%) showed mutations in katG and 29 (20.4%) in inhA. A high rate of hetero-resistance pattern was observed in rpoB gene (28.8%) and katG gene (9.8%). The most frequent mutation was S531L (81.1%) in rpoB region and S315T1 (100%) in katG gene.

Diagnostic performance of commercially available enzyme-linked immunosorbent assay kit in the diagnosis of extrapulmonary tuberculosis.

OBJECTIVES: Antibody based serodiagnosis tests for tuberculosis (TB) was used widely in developed and developing countries. Pathozyme Myco(®) immunoglobulin (Ig) M, IgA, and IgG were evaluated in pulmonary TB in many studies. MATERIALS AND METHODS: In this study we assessed this commercially available kit in detecting extrapulmonary TB (EPTB). RESULTS: A total of 354 subjects were recruited for the study, of which 217 (61.2%) were EPTB patients and 137 (38.7%) were subjects with no suggestive TB. The mean age was 29.7 ± 13.7 and 31.2 ± 15.2 years, respectively for two groups. Serum samples were tested for IgM, IgA, and IgG using Pathozyme Myco(®) IgM, IgA, and IgG kit. The individual specificity rates of IgM, IgA, and IgG were 70.8% (95% confidence interval (CI): 62.7-77.7), 77.3% (95% CI: 68.6-83.5), and 68.6%. (95% CI: 60.4-75.7); while their sensitivity was 29% (95% CI: 23.4-35.4), 24.4% (95% CI: 19.1-30.5), and 34.5% (95% CI: 28.5-41.1); respectively. CONCLUSION: The serological tests either singly or in combination failed or performed poorly to diagnose EPTB.

Poor performance of serological tests in the diagnosis of pulmonary tuberculosis: evidence from a contact tracing field study.

BACKGROUND: Delayed or missed diagnosis of TB continues to fuel the global TB epidemic, especially in resource limited settings. Use of serology for the diagnosis of tuberculosis, commonly used in India, is another factor. In the present study a commercially available serodiagnostic assay was assessed for its diagnostic value in combination with smear, culture and clinical manifestations. METHODOLOGY/PRINCIPAL FINDINGS: A total of 2300 subjects were recruited for the study, but 1041 subjects were excluded for various reasons. Thus 1259 subjects were included in the study of which 470 were pulmonary tuberculosis cases (440 of 470 were culture-positive) and 789 were their asymptomatic contacts. A house-to-house survey method was used. Blood samples were tested for IgM, IgA, and IgG antibodies using the Pathozyme Myco M (IgM), Myco A (IgA) and Myco G (IgG) enzyme immunoassay (EIA). Out of 470 PTB cases, BCG scar was positive in 82.34%. The Mantoux test and smear positivity rates in PTB cases were 94.3% (430/456), and 65.32% (307/470), respectively. Among the asymptomatic contacts, BCG scar was positive in 95.3% and Mantoux test was positive in 80.66% (442/548) contacts. No contact was found falsely smear positive. The sensitivity of IgM, IgA, and IgG EIA tests was 48.7%, 25.7% and 24.4%, respectively, while the specificity was 71.5%, 80.5%, 76.6%, respectively. Performance of EIAs was not affected by the previous BCG vaccination. However, prior BCG vaccination was statistically significantly (p = 0.005) associated with Mantoux test positivity in PTB cases but not in contacts (p = 0.127). The agreement between serology and Mantoux test was not significant. CONCLUSION: The commercial serological test evaluated showed poor sensitivity and specificity and suggests no utility for detection of pulmonary tuberculosis.

Use of immunoglobulin g avidity to determine the course of disease in visceral and post-kala-azar dermal leishmaniasis patients.

In the present study, anti-Leishmania immunoglobulin G (IgG) avidity was used to estimate the approximate time of disease manifestation. Significant differences (P < 0.0001) were found between the levels of anti-rKE-16 IgG avidity in leishmaniasis patients with recent and chronic diseases. More than 76% of patients with an illness duration of less than 6 months had avidity of less than 70%, 94% of patients had less than 80% avidity, and all (100%) patients with illness of more than 6 months had avidity values higher than 70%. The study showed that avidity could successfully be used to pinpoint the duration of leishmaniasis.