Diagnostic value of tachypnoea in pneumonia defined radiologically

Objective-To evaluate whether sensitivity and specificity of tachypnoea for the diagnosis of pneumonia change with age, nutritional status, or duratio n of disease. Methods-Diagnostic testing of 110 children with acute respiratory infection , 51 of whom presented with tachypnoea. The gold standard was a chest roent genogram. Thirty five children had a radiological image of pneumonia; 75 we re diagnosed as not having pneumonia. Sensitivity, specificity, and percent age of correct classification of tachypnoea, by itself or in combination wi th other clinical signs for all children, by age groups, nutritional status , and disease duration were calculated. Results-Tachypnoea as the sole clinical sign showed the highest sensitivity (74%) and a specificity of 67%; 69% of cases were classified correctly. Se nsitivity was reduced when other clinical signs were combined with tachypno ea, and there was no significant increase in correct classification, althou gh specificity increased to 84%. In children with a disease duration of les s than three days, tachypnoea had a lower sensitivity and specificity (55% and 64%, respectively), and a lower percentage of correct classification (6 2%). In children with low weight for age (< 1 Z-score), tachypnoea had a se nsitivity of 83%, a specificity of 48%, and 60% correct classification. Sen sitivity and specificity did not vary with age groups. Conclusions-Tachypnoea used as the only clinical sign is useful for identif ying pneumonia in children, with no significant variations for age. In chil dren with low weight for age, tachypnoea had higher sensitivity, but lower specificity. However, during the first three days of disease, the sensitivi ty, specificity, and percentage of correct classification were significantl y lower.