Tuberculin although projected as cure by Robert Koch, proved to be a good diagnostic tool for tuberculin hypersensitivity. Substantial inter and intra observer variations in size of induration by customary palpatory method are found. The ball point method has the inherent problem of marking the skin with ink and possible skin injury/irritation. Therefore a new method needs to be evolved for reading a tuberculin skin test.METHOD: A transparent scale was slided at an angle of 45 degree, starting 2cm away from the tuberculin skin test site. The scale stopped at the beginning of the site of induration due to resistance, slight pressure of the scale left the mark at the site of induration. This process was repeated to measure the transverse and horizontal indurations. The distance between the opposite marks was measured. Two readers measured the tuberculin readings using palpatory method, Ball point method and the New scale technique. They were blinded of each others readings.
By palpation method, measurement from the second observer was observed to be 4.5 mm less to 3.5 mm more than the measurement from the 1st observer. Whereas using Ballpoint method and the New scale method the inter observer variation was much less i.e. 3mm less to 2.5mm more. The area of imprecision was much less broad for the ballpoint pen method and the new scale method then the palpation method. Intra observer variation between Ballpoint pen and palpation or New Scale Method and palpation method was wide whereas difference between Ballpoint pen method and New Scale Method was narrow.
The inter and intra observer variations using New scale method are less then the customary palpatory method. The New scale method is useful for measuring tuberculin induration and eliminates the problem of soiling of the skin with the ink and possible injury while using ballpoint method.CLINCAL IMPLICATION: The New scale method can be employed for measuring tuberculin test indurations.
J. Kishan, None.