International controversies in interpreting the mantoux test with special reference to Saudi Arabia

Abstract

There is a general decline in the incidence of pulmonary tuberculosis (PTB) in developed countries, but infection by HIV has increased the incidence of PTB in affected countries. There are no signs of a similar decline in the incidence of PTB in some developing countries. The Mantoux technique for tuberculin testing continues to be among the effective diagnostic tools. The medical literature and textbooks of medicine show disagreement as to what constitutes a positive (specific) tuberculin reaction. This short review was intended to cite some examples of these differences and suggest a cutting point for use in the Kingdom of Saudi Arabia (KSA) based on the prevalence of environmental mycobacteria (Mycobacteria other than M. tuberculosis, MOTT). From this review different researchers within the KSA used different cut-off points at a time that the prevalence of MOTT was unknown, until 1993 when it was reported to be as low as 3.8/1000 population (based on sputum culture) and that the Kingdom is categorised among the middle PTB prevalent countries. Consequently, it seems appropriate to have 5 mm as a cutting point (positive) in all unvaccinated patients, particularly for those who were in contact with an infectious case, or having symptoms compatible with PTB, and also patients who were immuno-compromised as in HIV infection. This cut-off point can be revised and raised to 8 mm provided that the prevalence of PTB becomes lower than the current reported rate and MOTT prevalence remains low, but the 5 mm cutting point should remain for the aforementioned categories of patients.