An evaluation of bacterial antigen detection tests in CSF of children in developing communities

Abstract number: 1134_04_4

Revathi G.

Acute childhood meningitis is a life threatening condition often leaving the survivors with various degrees of neurological impairments including learning problems. Rapid diagnosis is imperative for timely and specific treatment. Bacterial antigen detection tests by latex agglutination (L.A. tests) have been available for several years for this purpose.

Objective:  

To analyze the available data on L.A. tests retrospectively to observe their performance as to their sensitivity specificity and cost effectiveness in a resource poor setting.

Methods:  

Data was collected from CSF samples analysed over 10 years(1993–2003). Sources were A. five post graduate thesis projects supervised by the author in teaching hospitals 1993 (360CSFs) 1995 (420 CSFs) in GTB hospital, Delhi, India. 1999, 2001, 2003 in Kenyatta National Hospital, Nairobi (480 CSFs) B.983 CSFs data was contributed by two private sector hospitals in Nairobi, the Aga Khan Hospital and the Gertrude Garden children's hospital where the author is a sessional pathologist. Data from A and B were separately analysed for comparison purposes. Selected case files were reviewed to compile the outcomes.

Results:  

A striking difference was seen between the data from A and B. Data A found the L.A test an important diagnostic tool, the high cost being seen as the only limiting factor. In contrast data B brought out serious draw backs as follows: 1. these tests were negative in early meningitis cases, 2. important and frequent bacterial pathogens like enterric bacilli and staphylococci cannot be diagnosed, 3. Haemophilli other than type B were missed. 4. 5% of positive L.A tests were non specific agglutinations 5. 8% were non specific cross reactions 6. sensitivity on the whole was no greater than that of gram staining 7.for detection of Strpt. pneumoniae and H. influenzae b gram stain was found to be more sensitive than L.A test.

Conclusions:  

To justify the high costs of L.A tests must be used very selectively. The tests are cost effective if used in situations like 1. high clinical suspicion of bacterial meningitis where gram stain is negative 2. partially treated meningitis where culture is likely to be negative 3. the results of L.A test can only augment other parameters of diagnosis rather than replacing them. 4. routine use of L.A tests on all CSFs is not cost effective in a resource poor setting. Author is deeply indebted to the post graduate students involved in this work.