Performance Evaluation Of Mdr-tb Color Plate Test For Rapid Detection Of Mycobacterium Tuberculosis And Multidrug-resistant Tuberculosis In Resource-limited Setting Addis Ababa Ethiopia

Background: Tuberculosis (TB) is a top global public health concern and its controllingrnprogram is chiefly hampered by diagnostic difficulties. Timely TB diagnosis and detection ofrndrug-resistant TB has a key significance for both patient management and the disease control.rnHowever, the commercially existing diagnostic tools are slow and unaffordable for resourcelimitedrnsettings.rnObjective: The current study was aimed to evaluate the performance of MDR-TB color platerntest (color plate test) for rapid concurrent detection of Mycobacterium tuberculosis (MTB)rnand multidrug-resistant TB (MDR-TB) directly from sputum specimens.rnMaterials and Methods: A cross-sectional, hospital-based diagnostic test evaluation studyrnwas conducted from March 2016 to February 2017 at All Africa Leprosy, Tuberculosis andrnRehabilitation Training Center (ALERT) hospital and St. Peter’s TB referral hospital inrnAddis Ababa, Ethiopia. The performance of the color plate test was prospectively comparedrnto the conventional Lӧwenstein-Jensen (LJ) culture and LJ indirect proportional drugrnsusceptibility test (DST), and the molecular GeneXpert MTB/RIF® assay. A paired morningrnexpectorated sputum samples were collected from 147 MDR-TB suspected patients using arnconvenience sampling technique in both hospitals. One of the two sputum samples is usedrnfor diagnosis purpose was tested directly by GeneXpert assay at each respective hospital’srnlaboratory and internally validated. But, the other sputa were refrigerated (4-80C) andrntransported to the Armauer Hansen Research Institute (AHRI) TB laboratory where the colorrnplate test and the conventional LJ culture and DST were conducted. Data were analyzedrnusing SPSS version 20, and kappa statistic was applied to test agreement between results ofrnthe three assays.rnResult: Of the 147 sputa, 137 (93.2%) sputa produced interpretable MTB detection resultsrnfor all the three assays and were included in the analysis. Compared to the conventional LJrnculture, color plate test was 93.6% sensitive and 98.3% specific while GeneXpert assay wasrn96.2% sensitive and 79.7% specific. Moreover, the color plate test had showed a strongrnagreement with both the conventional LJ culture (95.62%, kappa 0.9114) and GeneXpertrnassay (89.05%, kappa 0.7756) for the detection of MTB. Moreover, all conventional LJrnxvrnculture positives, 78 isolates were further subjected to conventional DST, and valid resultsrnobtained by color plate test and GeneXpert assay were 70 and 72 isolates respectively. Therncolor plate test demonstrated sensitivity of 91.3% and 93.6% specific for the detection ofrnisoniazid resistant MTB isolates with strong agreements (kappa 0.8399). However, thernaccuracy for detection of rifampicin resistance was suboptimal with low agreement (kapparnvalue of 0.08 and concordance 39%). The color plate test was also in low agreement with thernGeneXpert assay (38.57%, kappa 0.0773) for detection of RMP drug resistance. In thernpresent study, the results of color plate test can be obtained in a median time of 13 days whilernthe conventional indirect DST method requires an average of 50 days. Besides, the colorrnplate test is simple to use and the cost per test result also minimal relatively.rnConclusion: In this study, the color plate test was found to be a good alternative method forrnscreening of TB and selective drug resistant-TB in a timely and affordable way in resourcelimitedrnsetting despite limitations of the test need to be addressed before test approvals.rnKey Words: Color plate test, Conventional LJ culture, Diagnostic performance, GeneXpertrnassay, indirect proportional DST, Multidrug-resistant tuberculosis, Tuberculosis

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