Evaluation of GeneXpert MTB/RIF® Molecular Assay Using Urine Specimen for Diagnosis of Active Pulmonary Tuberculosis from Sputum Scarce Patients in Ethiopia

Backround: Tuberculosis (TB) is one of the leading causes of death in low-income countries especially among TB/HIV co-infected patients. Due to the weak health care system and difficulty of getting sputum specimens from TB-HIV co-infected patients and children, the rate of undiagnosed TB cases is very high in most high TB burden countries. Therefore, we evaluated the performance of GeneXpert MTB/RIF using urine as alternative specimen for the sputum scarce patients.

Methodology: A total of 150 clinically TB suspected cases (75 sputum scarce cases and 75 cases who were capable to provide sputum) provided a morning urine specimen and 75 cases who were able to provide sputum also provided sputum. Urine & sputum specimens were analyzed by using GeneXpert MTB/RIF, culture and Ziehl-Neelsen (ZN) microscopy methods.

Result: Of the 150 urine and 75 sputum specimens tested, we found 5 (3.3%) urine and 26 (34.6%) sputum specimens positive by GeneXpert MTB/RIF and culture. Moreover, we found 1 (0.7%) urine and 1 (1.3%) sputum positive by GeneXpert MTB/RIF only. The sensitivity and specificity of GeneXpert MTB/RIF using urine were 100% and 99.3% (95%CI:4-100%) respectively, in addition, using sputum specimens it had 100% sensitivity and 98.0% (95% CI: 94.8-100%) specificity by using culture results as reference test. The overall performance agreement between GeneXpert MTB/RIF and culture using urine and sputum specimens were 99.3% (95% CI: 97.4-100%) and 98.7% (95% CI: 96.1-100%) respectively. In general, our finding showed that the total TB confirmed cases were increased from 26 (17.3%) to 30 (20.0%) by using urine as an alternative specimen.

Conclusion: A good sensitivity and specificity of GeneXpert MTB/RIF were observed using urine specimen, thus, urine can be used as an alternative specimen for diagnosis of PTB from sputum scare patients using GeneXpert MTB/RIF Assay.