Evaluation of two novel Ziehl-Neelsen methods for tuberculosis diagnosis

Currently, the diagnosis of tuberculosis (TB) in Ghana relies on direct sputum smear, Ziehl- Neelsen (ZN) staining method. This method has low sensitivity and poses some health risks. The study was to compare the, direct sputum smear, (ZN) staining method against two newer ZN methods; 1% Sodium hypochlorite (NaOCL)-xylene floatation and 1% NaOCL sedimentation methods, to determine the most sensitive and the safest

A prospective descriptive study involving 150 adult patients attending Komfo Anokye Teaching Hospital, Kumasi, Ghana suspected of pulmonary tuberculosis, using the three ZN microscopy methods: direct sputum smear, 1% NaOCL sedimentation, and 1% NaOCL-xylene floatation, for the detection of acid fast bacilli (AFB). Sputum culture on Lowenstein-Jensen (LJ) slopes was used as the gold standard for determining the sensitivity and specificity rates.

The sensitivity rates of NaOCL sedimentation, NaOCL-xylene floatation and direct smear methods were 77.2%, 71.8% and 66.3% respectively. The specificity rate was 95.9 % for all three methods. Whereas the difference between the NaOCL sedimentation and the direct smear methods was statistically significant (P= 0.0446), that between the NaOCL-xylene floatation and direct smear was not (P=0.1788).

In spite of the cost of chemicals, the hypochlorite sedimentation method was found to be the most accurate and the safest.