Cut-off value of mantoux induration in tuberculous children in R. Macedonia and their nutritional status.

INTRODUCTION The interpretation of the Mantoux test, as well as knowledge of factors that affect the test's induration size, is significant for the early diagnosis of tuberculosis in children. AIMS To determine the Mantoux test induration cut-off size which distinguishes between positive and negative results in Macedonian children suffering from tuberculosis. To find whether there is any correlation between the nutritional status (malnutrition) and the Mantoux induration size. MATERIALS AND METHODS A retrospective and descriptive study was carried out in 270 patients up to 14 years old with diagnosed tuberculosis, treated during the period of 2003-2007 in the Pediatric Tuberculosis Department at the Kozle Institute for Respiratory Diseases in Children, Skopje, Macedonia. The cut-off value of the Mantoux test induration size was determined by analysis of the test results distribution. The nutritional status was calculated as the weight for age standard (z-score). Correlation between the TST results and the nutritional status was calculated with Pearson's coefficient of correlation. RESULTS Two hundred and seventy (270) children with tuberculosis were included in the study. The lung form of tuberculosis was present in 87.8% of the children. 53.7% of the patients were male, and 46.3% were female. The age group of 1-2 years was the most numerous (15.2%), followed by the group aged 7-8 years (10.4%). 33 children (12.2%) were undernourished (z-score<-2). The Mantoux test induration size was in the range of 0 to 32 mm, with an average of 13.4 mm. The distribution of the frequencies of the indurations had a bimodal form, with the primary mode at 0 mm, the secondary mode at 15-19 mm, and antimode at 5-9 mm. The Mantoux test had a sensitivity of 82.5%, specificity of 62%, positive predictive value of 68.46% and negative predictive value of 78.61%. Pearson's coefficient of correlation (r) of 0.175 showed a weak positive correlation between the results of TST (induration size) and the nutriational status. CONCLUSIONS The cut-off value of the induration which distinguishes negative from positive Mantoux reaction was 5 mm. The interpretation of the test is recommended to be carried out depending on the risk factors for TB development, which surround the children. The Mantoux test in malnourished children should be interpreted with caution.