GENE XPERT MTB/RIF SPECIFICITY AND SENSITIVITY IN TUBERCULOSIS DIAGNOSIS USING URINE SAMPLES FROM HIV PATIENTS WITH SIGNS OF TUBERCULOSIS AT THE MOI TEACHING AND REFERRAL HOSPITAL IN WESTERN KENYA

The Mycobacterium tuberculosis/Rifampin (Xpert MTB/RIF) has been reported to be a fast molecular tool in the determination of the existence of mycobacterium tuberculosis DNA in mucoid (sputum) samples. However, the deployment of Gene Xpert for testing non-sputum clinical samples in the diagnosis of suspected tuberculosis in western Kenya population has not been evaluated. We are reporting on Specificity and sensitivity of urine Gene Xpert MTB/RIF from HIV patients clinically suspected of tuberculosis. Urine analysis from 158 HIV patients suspected of TB with CD4+ count <200 cells/mm3 were done. Among the female 11% and 15% were positive based on urine Gene Xpert MTB/RIF and urine LAM respectively with a majority (71%) having CD4 >100 ˂200 cells/mm. Sensitivity and specificity of urine Xpert was equated to smear microscopy, at the same time with urine culture. Sensitivity of urine Xpert against sputum microscopy was 17%, with a positive predictive value of 29%. Specificity of urine Xpert against sputum microscopy was 91%, with a negative predictive value of 83%. Stratified by CD4 categories, the test showed to be more sensitive (30% vs 11%) and specific (92% vs 89%) in patients with CD4≤100˂200 cells/mm3 compared to those with CD4>100 ˂200 cells/mm3 respectively. The data suggest that Gene Xpert assay is a sensitive and specific tool that rapidly identifies Mycobacterium tuberculosis using urine as a sample in immunocompromised patients.