Assessment of Diagnostic Performance of Abbott Real Time PCR for the Detection of Smear Negative Pulmonary Tuberculosis at Ethiopian Public Health Institute, Addis Ababa Ethiopia

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Addis Ababa University


Background: In 2016, an estimated 10.4 million people developed TB and of these more than 1.6 million died from the disease, 374,000 (22%) of whom were HIV-positive. In most of the high burden of tuberculosis but resource poor countries, microscopy method issued in which acidfast bacilli are detected in smear using a light microscope. However, smear microscopy is not so reliable. As of other most advanced tests, molecular techniques still not implemented in developing countries including Ethiopia. To improve MTB case detection rate, there is a need to introduce and implement rapid batch testing molecular methods in Ethiopia. Objective: The objective of this study was to assess the performance characteristics of Abbott real time for the diagnosis smear negative MTB Methods: Both prospective and retrospective cross-sectional survey was carried out to enroll 127 study participants’ records along with left over sputum specimens in Addis Ababa, EPHI national TB/HIV laboratories from March to May 2018. Performance characteristics including sensitivity, specificity and predictive values was calculated by using SPSS version 23 with 95% CI. For all statistical significance tests, the cut-off point was 0.05 and p < 0.05 considered as statistically significant association with testing performance. Results: Diagnostic sensitivity of Abbott real time for the diagnosis of smear negative was 82.9% and specificity exhibited 89.1%. Drug susceptibility testing demonstrated diagnostic specificity of 87.5% and 100% for INH and RIF respectively. Abbott real time performance significantly and negatively associated with month of treatment [Adjusted OR (95%CI) = 0.01 (0.00. 0.41)] for 1st to 6th month, 0.005 (0.00, 0.20) for 7th to 12th months and 0.001 (0.00, 0.90) for the clients on treatment for more than a year Conclusions: The diagnostic sensitivity of the method for identification of MTB and drug resistancesensitivity and specificity similar with the previous similar studies. The method exhibited lower specificity for the diagnosis smear negative MTB cases. The finding also revealed the specificity of Abbott real time the lowest as of other molecular methods for the diagnosis of smear negative MTB cases who are on MTB treatment. Therefore, we strongly recommend not to use the method for all follow-up MTB cases except zero month and further investigation should be continued to explain exhaustively the effect of explanatory variables on Abbott MTB performance.



Abbott real time PCR, MTB, Sensitivity, Specificity