Journal of Diagnostic Techniques and Biomedical Analysis

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

Eyob Abera Mesfin, Dereje Beyene, Abreham Tesfaye, Desalegn Addise, Miskir Amare, Biniyam Dagne, Ephrem Tesfaye,  ZelalemYaregal and Belay Tessema

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.