Sero diagnosis of tuberculosis in children using two ELISA kits

Abstract

Abstract. The diagnosis of childhood tuberculosis is based on circumstantial evidence in the absence of a gold standard in the majority of cases. Sero-diagnosis offers scope for an early diagnosis in a variety of clinical conditions and is simple to perform. A number of mycobacterial antigens have been used for antibody detection assays and several are available as kits in the market. This study was done to evaluate the value of antibody detection kits (ELISA) against the A60 antigen and 38kDa antigen of Mycobacterium tuberculosis in the diagnosis of childhood tuberculosis at the outpatient department of the Institute of Social Paediatrics, Government Stanley Hospital in collaboration with Tuberculosis Research Centre, Chennai. Thirty five children with pulmonary tuberculosis, 7 with TB lymphadenitis and 22 healthy controls were studied. In addition to routine investigations including gastric lavage for AFB culture, serum antibodies against the A60 and 38kDa antigens were assayed using commercially available ELISA kits. With A60, IgM serum levels were positive in 74% of pulmonary TB cases, 57% of TB lymphadenitis cases and 50% of controls. A60 IgG was positive in 17% of pulmonary TB, 86% of TB lymphadenitis and 14% of controls. The 38 kDa IgG antibody was positive in 37% of pulmonary and 86% of TB lymphadenitis cases and 27% of controls. Among 10 culture confirmed cases, A60 IgM was positive in 8, A60 IgG in 3 and 38kDa IgG in 5 patients. The sensitivity of the tests ranged between 29% and 71% and specificity between 50% and 86%. Although the numbers are small, the results suggest that serodiagnosis using the currently available antigens of M. tuberculosis is unlikely to be a confirmatory test for tuberculosis in children. (Indian J Pediatr 1999; 66 : 837-842)

Study of the antibody response against Mycobacterium tuberculosis antigens in Warao Amerindian children in Venezuela

“…Bearing in mind that the sensitivities of culture and smear drop precipitously when applied to children, and other diagnostic test/criteria take on greater importance such as serological tests, especially combined tests (Alifano et al 1996, Gupta et al 1997, Swaminathan et al 1999, Pottumarthy et al 2000, Imaz et al 2001), the present ), anti-PPD IgG ( ), anti-PPD IgE ( ), anti-38 kDa sIgA ( ). The evaluation of positive sera was based on a positive score represented by optical density (OD) values above the cut-off point of the mean value plus 2 standard deviations of sera from a healthy control group (n = 38) from Caracas, the capital of Venezuela.…”

“…The use of ELISA for immunodiagnosis of TB has shown that the humoral response to mycobacterial antigens is low in children, especially when combined responses against antigens or specific antibodies are not used (Starke 1993, Swaminathan et al 1999, Sant'Anna et al 1999. Non-recombinant and recombinant antigens of Mycobacterium tuberculosis such as purified protein derivative (PPD) and 38 kDa and HSP60, respectively have been used for the serodiagnosis of TB.…”

Antibody Responses to Mycobacterial Antigens in Children with Tuberculosis: Challenges and Potential Diagnostic Value

“…Overall, Ab responses to mycobacterial antigens in childhood TB varied widely, with sensitivities and specificities ranging from 14% to 85% and from 86% to 100%, respectively. Even when evaluating the same commercially available test, such as the Anda-TB Kit (Anda Biologicals, Strasbourg, France), sensitivities for detecting childhood TB ranged from 14% to 71% and specificities ranged from 50% to 100%, with part of the variability being due to the different isotypes tested (22,24,29,66,67) (Table 1). Such wide ranges in accuracy of serologic assays have also been observed in adult TB, although many of the reasons for this variability differ (reviewed in references 62 to 64).…”

“…Thus, similar to studies with PPD or mycobacterial sonicates, studies with A60-based assays evaluate serological responses to a broad mixture of mainly nonspecific native mycobacterial antigens, which may result in considerable cross-reactivity. Five studies have evaluated IgG, IgA, and IgM responses to A60 in children using the Anda-TB kit, with reported sensitivities ranging from 14% to 71% and specificities ranging from 50% to 100% (22,24,29,66,67) (Table 1).…”

A Critical Appraisal of the Ban on Serological Tests for Tuberculosis Usefulness of Serological Monitoring of Tuberculosis Antibodies during the Treatment of TB Patients

“…I report here 7 authors who published on this subject [22][23][24][25][26][27][28]. As indicated above, some of these studies are negative, as they report poor sensitivity in primary cases.…”