Use of GeneXpert and the role of an expert panel in improving clinical diagnosis of smear-negative tuberculosis cases

Abstract

SettingA 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.ObjectivesTo 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.DesignThis 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.ResultsThirty-two percent (48/152) of the sample were Xpert positive and 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 the GeneXpert results the Expert panel’s sensitivity for active tuberculosis was high (97.5%, 39/40), specificity was low (40.2%, 35/87).ConclusionUsing 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 realtime 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.…”

Deep Learning–based Diagnosis of Pulmonary Tuberculosis on Chest X-ray in the Emergency Department: A Retrospective Study

“…To the best of our knowledge, our CAD algorithm may be the first to detect both bacteriologically confirmed and clinically diagnosed PTB. As there were some overlaps in CXR findings between these two types of PTB [ 46 ], the only way to differentiate one from the other is by collecting specimens for examination, such as a sputum smear. Since timely isolation and prompt examination is necessary for patients with both types of PTB diagnosis, we selected both as the target labels in our study.…”

Evaluation of the use of GeneXpert MTB/RIF in a zone with high burden of tuberculosis in Thailand

“…In such circumstances, it could be said that the physicians did not completely rely on GeneXpert MTB/RIF as a “rule-out test.” A study in the Philippines showed a higher rate of registered patients for PTB treatment among patients with presumptive TB with negative smears and negative GeneXpert MTB/RIF results (89/152 cases, 58.5%). The physicians in the Philippine also diagnosed and treated PTB cases based on clinical diagnosis and other evidence regardless of the negative GeneXpert MTB/RIF results [ 30 ]. As claimed in Part II of this study, a physician said “I usually consider clinical signs together with the results of GeneXpert to start TB treatment , ” while another mentioned that “GeneXpert is a facilitating tool to confirm TB diagnosis among CXR abnormal cases .…”

“…In areas with a high prevalence of RR, GeneXpert MTB/RIF-based detection could be a representation of MDR-TB [ 24 , 34 – 36 ]. According to the recommendations of CDC, RR is a predictor of MDR-TB because RR coexists with isoniazid (INH) resistance, and thus rapid RR diagnosis would enable the patients with TB to begin successful MDR-TB treatment much earlier than they would if they were awaiting results from other drug susceptibility tests [ 30 ]. In this study, we collected data from patients at high risk of MDR-TB who had CXR results indicative of PTB.…”

“…Likewise, negative smears with positive GeneXpert MTB/RIF results were reported in a study conducted in a hospital in India (34.9%) and in a study conducted in two hospitals in the Philippines (31.5%). The incidence of overdiagnosis will be greatly reduced when a decision is made based on the results of GeneXpert MTB/RIF [ 30 , 43 ]. As noted in the in-depth interview, “It makes things easier to consider TB disease even when the patients have no signs or symptoms” and “ the GeneXpert could help as a tool to reveal the TB strains even when the direct smear is negative , so we do not miss a case .…”