Increased Diagnostic Yield of Tuberculous Serositis by Using Serous Fluid Drainage Flocky Precipitate (SFDFP) as a Testing Sample

Abstract

A definitive diagnosis of tuberculosis serositis (TS) is still challenging. Our preliminary practice found that Serous Fluid Drainage Flocky Precipitate (SFDFP) was a useful testing sample to diagnose TS. We designed this study to assess the diagnostic performance of SFDPF for TS compared with conventional bacteriology methods on serous fluid (SF). A cohort study was conducted from July 2014 to April 2016. Patients with suspected TS were consecutively screened. SF and SFDFP were collected and tested by Ziehl-Neelsen stain, MTB culture, and Xpert/RIF assay. We compared the diagnostic performance of SF and SFDFP in several test settings. Through this study, 85 patients were enrolled, of whom 70 (82.4%) were confirmed TS or highly probable TS, 13 (15.3%) were none-TS and 2 (2.4%) indeterminate results were ruled out. The overall sensitivity using both SFDFP and SF was significantly higher than each (60% vs. 48% and 41%, p < 0.05). SFDFP and SF samples had similar diagnostic performance (p < 0.05). No false positive was detected in this study. We concluded that SFDFP is a reliable testing sample for diagnosing tuberculous serositis. SFDFP may significantly improve the diagnostic yield as a supplement to conventional tests.

Figure 1

Serous Fluid Drainage Flocky Precipitate samples extracted from serous fluid. This sample can be easily collected from an overnight drainage bag and has a unique cotton-like formation (a,b). Samples can be stained and examined by histopathological methods to differentiate malignant tissue (c) and MTB infection (d). Staining methods of c and d were hematoxylin and eosin (HE) and acid-fast staining respectively.

Figure 2

Specimen testing, participant flow and basic characteristics, enrollment and exclusion from analysis eligibility. Participants were consecutively recruited and screened at inpatient facilities in Shanghai Public Health Clinical Center with: (i) clinical suspiciion of tuberculous serositis; (ii) serous effusion over 300 ml and well collected; (iii) HIV test negative; and (iv) written informed consent obtained. The 13 second Xpert testing results were extracted from clinical data retrospectively to assess the value of the repeated test. The results of the repeated test were not included in final analysis.