Temperature affects the results of the glutaraldehyde test in the diagnosis of pulmonary tuberculosis

SETTING: Subjects attending the District Tuberculosis Clinic and a Teaching Hospital in Jodhpur were studied at the Desert Medicine Research Centre, Jodhpur.

OBJECTIVES: To confirm the effect of temperature on the results of the blood glutaraldehyde test (GT) and to examine the sensitivity and specificity of the restandardised test procedure.

DESIGN: Blood glutaraldehyde gelification time (BGGT) was compared, in the same blood samples, at 19, 22 and 25°C and after storage at 1) room temperature and at 2) 2–8°C for 3–5 h, using the paired t-test. After restandardisation of the procedure, the GT was carried out on 88 sputum culture-positive cases with pulmonary tuberculosis (PTB) and 182 controls. The technician was blinded to patient information.

RESULTS: BGGT significantly varied with the temperature of the water bath and the temperature at which blood samples were stored before testing. When the test was carried out in the water bath at 22°C after storing blood for 3–5 h at 2–8°C, as per the restandardised procedure, the specificity of GT was 96.2% (95%CI 93.36–98.95) and the sensitivity was 84.1% (95%CI 76.45–91.73).

CONCLUSION: Restandardised GT is a reliable, simple, easy, rapid, inexpensive and user-friendly test for diagnosis of PTB which does not require sophisticated laboratory equipment.