Score for pulmonary tuberculosis in patients with clinical presumption of tuberculosis in a low-prevalence area

Sampling strategy for bacteriological diagnosis of intrathoracic tuberculosis

BACKGROUND

Pulmonary tuberculosis (TB) is the most frequent site of TB and the one leading its spread worldwide. Multiple specimens are commonly collected for TB diagnosis including those requiring invasive procedures. This study aimed to review the sampling strategy for the microbiological diagnosis of pulmonary TB.

METHODS

A retrospective analysis of collected samples from September 1st 2014 to May 1st 2016 in the Bacteriology laboratory of Pitié-Salpêtrière Hospital (Paris, France) was performed. All the samples collected in patients aged over 18 years for the bacteriological diagnosis of pulmonary TB were included.

RESULTS

A total of 6267 samples were collected in 2187 patients. One hundred and twenty-six patients (6%) had a culture confirmed pulmonary TB. Among them, multiple sputum collections were sufficient for TB diagnosis in 63.5%, gastric lavages permitted to avoid bronchoscopy in only 7.1%, and bronchoscopy was necessary in 29.4%. The culture positivity of sputa (8.6%) was higher than that of bronchial aspirations (3.1%), bronchiolo-alveolar lavages (BAL) (2.3%) or gastric lavages (4.8%) (P<0.001). From its 70.0% theoretical PPV value, the 46.1% selection in bronchial aspirations allocated to molecular test increased PPV up to 88.9%.

CONCLUSIONS

Based on our data, we suggest to collect sputum consistently. If smear negative a bronchoscopy should be performed and molecular diagnosis be performed on a subset of bronchial aspirations based on expertise of the bronchoscopist.

Pulmonary tuberculosis: Evaluation of current diagnostic strategy

OBJECTIVE

To identify tools that will result in faster diagnosis, making the current pulmonary tuberculosis strategy more efficient.

PATIENTS AND METHODS

A 4-year (2015-2018) retrospective study. The gold standard for diagnosis was a positive culture from a respiratory specimen. All sputum, fibroscopy and post-fibroscopy specimens (for smear negative patients) were collected. Each specimen was analyzed through smear examination and culture. All nucleic acid amplification testing results were included. Analyses looked at the incremental yield of positive cases of each successive specimen collection, and time to diagnosis.

RESULTS

A total of 354 patients had at least one positive culture. Sputum allowed a diagnosis in 92% of cases (including a gain in sensitivity of around 7% for the third sputum specimen), with 160 smear-positive patients (45%). Among smear-negative patients, 109 underwent a fibroscopy procedure (culture sensitivity of 75%), and 59 had a post-fibroscopy specimen collected, which together identified the rest of the patients (8%). Molecular testing was used in 237 specimens. Median time to diagnosis was 11 days, which was significantly reduced among smear-negative patients when molecular testing was used (P<0.001). Shortening the delay between sputum specimen collections did not alter procedure sensitivity.

CONCLUSIONS

We identified several aspects of the French tuberculosis diagnosis algorithm that could be improved, and posed the basis for a prospective study. Centers in higher incidence areas could benefit from a dedicated, predefined procedure exploring suspicions of tuberculosis. A high suspicion score of tuberculosis could drive the reasoned use of molecular testing in such settings.