An alternative 1-day smear microscopy protocol for the diagnosis of pulmonary tuberculosis

This study was undertaken to assess the feasibility of diagnosing pulmonary tuberculosis (PTB) by collecting two sputum samples on a single day (1-day protocol), and to compare this protocol with the national policy of collecting two samples on consecutive days (2-day protocol).

A total of 513 individuals with cough that had persisted for more than 2 weeks were screened for PTB by collection of three sputum samples: a spot sample on the first day, a sample collected 1 h after the first sample and a sample collected the following morning. For the 2-day protocol, the diagnostic performance of the first and third samples was considered, while the 1-day protocol was evaluated using the two samples collected on the first day. Staining and microscopy were performed in a blinded manner by two different technicians.

Of the 513 patients, 40 defaulted on the second day. Of the total number of patients recruited, 124 (24.2%) were smear-positive. Using the 2-day protocol, 121 patients (97.6%) were identified as smear-positive, whereas with the 1-day protocol 118 patients (95.2%) were identified as smear-positive (P = 0.3). Of the patients who defaulted, seven (17.5%) were smear-positive. Comparison of the variation in results indicated that collection of a morning sample on the second day provided no significant benefit over collection of a second spot sample on the first day.

As the 2-day protocol did not show a statistically significant difference in diagnostic performance compared with the 1-day protocol, the latter may be adopted as an alternative protocol, particularly for patients who are more likely to default.