Use of GeneXpert and the Role of an Expert Panel in Improving Clinical Diagnosis of Smear-Negative Tuberculosis Cases

Abstract

Setting A high proportion of notified tuberculosis cases in the Philippines are clinically diagnosed (63%) as opposed to bacteriologically confirmed. Better understanding of this phenomenon is required to improve tuberculosis control. Objectives To determine the percentage of Smear Negative Presumptive Tuberculosis patients that would be diagnosed by GeneXpert; compare clinical characteristics of patients diagnosed as tuberculosis cases; and review the impact that the current single government physician and a reconstituted Tuberculosis Diagnostic committee (Expert Panel) may have on tuberculosis over-diagnosis. Design This is a cross-sectional study of 152 patients 15-85 years old with two negative Direct Sputum Smear Microscopy results, with abnormal chest X-ray who underwent GeneXpert testing and review by an Expert Panel. Results 31% (48/152) of the sample were Xpert positive. 93% (97/104) of GeneXpert negatives were clinically diagnosed by a Single Physician. Typical symptoms and X-ray findings were higher in bacteriologically confirmed tuberculosis. When compared to GeneXpert results, the Expert panel’s sensitivity for active tuberculosis was high (97.5%, 39/40) but specificity was low (40.2%, 35/87). Conclusion Using the GeneXpert would increase the level of bacteriologically confirmed tuberculosis substantially among presumptive Tuberculosis. An Expert panel will greatly reduce over-diagnosis usually seen when a decision is made by a Single Physician.

Utility of the GeneXpert Mycobacterium tuberculosis/Rifampin (MTB/RIF) Assay on Paraffin-Embedded Biopsy Tissue Samples for Detecting Tuberculosis; Comparison With Histopathology

“…The Xpert Mycobacterium tuberculosis/Rifampin (MTB/RIF) assay is a qualitative nested real-time polymerase chain reaction (PCR) performed on the GeneXpert instrument system [ 2 ]. The Xpert MTB/RIF assay was primarily intended for sputum samples, and various studies have documented the diagnostic reliability of Xpert MTB/RIF for sputum and pus samples [ 3 , 4 ]. Although, the utility of this technique for detecting MTB in sputum and pus samples is well established, however, the usefulness of GeneXpert on biopsy samples is still a matter of debate.…”

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