Specificity and sensitivity of chest radiographs in the diagnosis of paediatric pulmonary tuberculosis and the value of additional high-kilovolt radiographs
Tuberculosis (TB) remains the most common notifiable infectious disease in South Africa. The diagnosis of pulmonary TB in children is often very difficult because of the non-specific radiological signs and inter-observer variation in the interpretation of radiographs. The frontal high-kilovolt (kV) radiograph has been used to assess the effect of TB adenopathy on the tracheobronchial tree and to detect endobronchial lesions. The aims of the present study were to assess the specificity and sensitivity of chest radiographs in the diagnosis of pulmonary TB and to assess whether the addition of the high-kV radiograph affects these parameters. The study group consisted of paediatric patients suspected of having pulmonary TB over a 6-year period. These patients had clinical, bacteriological and radiographic examinations. Radiographs were examined by one experienced radiologist in two sittings separated by a 6-week interval. On the first sitting, only standard radiographs were examined and, on the second sitting, these were supplemented with high-kV radiographs. Differences in the detection of each recognized radiological feature of pulmonary TB before and after the addition of the high-kV film were analysed for statistical significance. The frequency of radiographic findings in our study compared favourably with other reports. No statistically significant differences for the detection of radiographic features consistent with pulmonary TB, or for the diagnosis of pulmonary TB, were demonstrated between the two sittings. Specificity increased from 74.4% to 86.6% with the addition of the high-kV view and sensitivity remained constant at 38.8%. The present study does not support the routine use of the frontal high-kV radiograph for the diagnosis of pulmonary TB. This paper also confirms the findings of others, that standard chest radiographs are a poor indicator of pulmonary TB in children.