TITLE:
Value of Repeated Direct Smear Sputum Examination in the Diagnosis of Pulmonary Tuberculosis
AUTHORS:
Wafaa Ali Hassan, Amany Omar, Saher Khalil, Atef Farouk Al-Qarn
KEYWORDS:
TB, Direct Smear, Value
JOURNAL NAME:
Open Journal of Respiratory Diseases,
Vol.4 No.2,
April
11,
2014
ABSTRACT: Introduction: The examination of three sputum samples per suspect has been severely criticized
from a public health viewpoint and several recent trials have documented the relative inefficiency
of the third smear and the necessity for confirmation of a positive smear has also been contested.
Aim: This study, undertaken in Qena, Egypt, aimed to determine the usefulness of examining the
second and third direct smear microscopy (DSM) specimen in the diagnosis of pulmonary TB. Patients
and methods: A retrospective study using record review at TB outpatient clinic; Qena Chest
Hospital, Egypt, was done from 2010-2013. Direct smear results were collected as one of the following
combinations PNN, PPP, PPN, PNP, NNP, NPP, and NPN, NNN, where N is a negative and P a
positive smear. The proportion of positive, first, second and third specimen were calculated. Cases
were considered positive having at least one positive smear confirmed by another positive one in
the absence of sputum culture. Results: Out of 9420 recorded suspects, 719 of them were positive,
so smear positivity was 7.6%. The majority of them were diagnosed from the first sample (96.4%).
For only 3.6% (26 of 719), the second smear was positive and a third specimen was required (NPP)
to make a definitive diagnosis of TB. No recorded isolated positive or negative smears in the third
sample (NNP or PPN). Conclusions: These data indicated that, in our locality with limited financial
resources, the incremental yield of a second sputum direct smear examination was low, and the
third one was negligible indicating that examination of two sputum samples is enough among
pulmonary TB patients. A third sample is required only as confirmatory if the second sample was
positive. Smear microscopy can be substantially simplified with favourable resource implications.