MATERIALS AND METHODS

Study design and study period

A cross-sectional descriptive study was carried out during 2017-2018.

Study population 

A total of 279 HIV patients with clinically diagnosed TBM attending Waibagi, Thakayta and Mingaladon Specialist Hospitals during the study period.

Inclusion criteria 

HIV-seropositive patients with clinically diagnosed TBM (both male and female, 18 years age) who gave written informed consent.

Exclusion criteria 

Critically ill patients, patients with signs of intracranial space occupying lesions or local infection in lumbar space 

Socio-demographic and clinical data 

After taking the informed consent, the relevant socio-demographic data and clinical data regarding the symptoms and duration of disease, previous history of anti-TB treatment and duration, concomitant diseases, history of HIV infection, investigations such as CD4+ count, Xpert MTB/RIF results, other laboratory tests etc., were collected. 

Laboratory procedures 

Sample collection

After obtaining informed consent, demographic and clinical data had been noted in proforma. Lumber puncture was carried out under aseptic condition according to the standard procedure and CSF pressure was measured by Spinomanometer. CSF was collected by three sterile-leak proof tubes, one for routine CSF analysis and microscopy, second tube for routine Xpert MTB/RIF assay and the extra tube about 0.5 ml for LAM-LFA and TB culture.

CSF LAM-LFA

One drop (about 60 ul) of CSF was applied to LAM-LFA test strip (Lateral-flow TB LAM antigen testing, Alere, Waltham, MA, USA). After 15 minutes, 2 experienced laboratory technicians independently read the test strip by comparing the LFA test result to the manufacturer-supplied reference card. The results were calculated the sensitivity, specificity, PPV, and NPV of LAM lateral flow antigen test for definite TBM, using no TBM as the denominator.⁸

CSF routine examination, microscopy and CSF Xpert MTB/RIF  

Routine examination of CSF (eg. protein, sugar, cells count, Ziehl-Neelsen staining and Indian ink staining) was carried out. CSF was also tested by Xpert MTB/RIF to detect TB and rifampicin resistance. The laboratory results were recorded in the proforma.

CSF Mycobacterium tuberculosis culture and anti-TB drug susceptibility testing (DST)

The CSF samples were inoculated onto Lowenstein-Jensen solid medium and incubated at 37°C. Tubes were checked at weekly intervals until 12 weeks for the colonial morphology and growth reading.9 DST of first-line anti-TB was performed by solid culture-based proportion method and DST of pyrazinamide and second line anti-TB drugs was performed by liquid culture-based MGIT system.10 Definite TBM was defined as culture positive for TB and/or a positive CSF Xpert MTB/RIF result.

Statistical analysis

The data were analyzed using SPSS version 23 statistical software. Statistical comparison between various groups was made using Fisher’s exact test when appropriate and their 95% confidence interval were used to measure the strength of associations. The level of significance was set as p0.05.

Ethical consideration 

This study was approved by the Protocol Academic Board, Department of Medical Research.