Utility of GeneXpert and Cytomorphology in the Diagnosis of Extrapulmonary Tuberculosis at Kenyatta National Hospital in Kenya. (21st September 2018)

• Record Type: Journal Article
• Authors: Manyepa, Mespa; Rogena, Emily; Oyugi, Julias; Rioki, Josephine; Ngayo, Musa Otieno
• Is Part Of: American journal of clinical pathology. Volume 150(2018)Supplement 1
• Page Start: S78
• Page End: S78
• Publication Date: 2018-09-21
• Subjects: Diagnosis, Laboratory -- Periodicals; Pathology -- Periodicals; 616.07
• DOI: 10.1093/ajcp/aqy094.188
• Languages: English
• ISSNs: 0002-9173

Abstract

Abstract: Objectives: In this study, we evaluated the performance of cytomorphology, GeneXpert, and ZN for the diagnosis of cases suspected of EPTB referred to the fine-needle aspirate clinic (FNA) at Kenyatta National Hospital (KNH), Nairobi, Kenya. Methods: FNAs were collected from presumptive EPTB cases. Two smears were prepared from each aspirate and processed for cytology and conventional ZN microscopy smear. The remaining aspirate was treated with 2 mL of 20% NaOH and allowed to stand for a minimum of 30 minutes. The bacilli were then floated using 0.5 ML of xylene and scooped and transferred to 2 mL of normal saline and used for GeneXpert test. The performance of the tests was calculated using R software version 3.2.2. Using the Bayesian method and latent class analysis model, the software was able to calculate the sensitivity, specificity, negative predictive value, and positive predictive value of the tests in the absence of a gold standard or reference standard test. Results: There were 50 TB suspected cases recruited in this study, but only 43 were analyzed. The mean (SD) age was 26.74 (14.146) years, with a range of 2 to 56 years. Out of the 43 TB suspected cases analyzed, 10 (23.3%) were confirmed by GeneXpert, 25 (58.1%) were suggestive for TB by cytomorphology, and one (2.3%) was positive by ZN microscopy. GeneXpert agreement with cytomorphology was fair (Cohen's κ coefficient = 0.358; P = .002); ZN microscopy had slight agreement, which was not significant (κ = 0.146; P = .066). Sensitivity and specificity of tests in this study sample size were cytomorphology, 25 (56.9%) and 18 (36.7%); ZN, 1 (4.9%) and 42 (94.4%); and GeneXpert, 10 (25.6%) and 33 (66.2%). Conclusion: Our findings indicated that GeneXpert MTB/RIF test is a useful tool for the detection of MTB with reasonable sensitivity and specificity for extrapulmonary tuberculosis with good performance.