Assessment of X-ray readers in TB prevalence surveys.

Gopi, P.G.; Vasantha, M.; Muniyandi, M.

Journal of Communicable Diseases; 2010; 42; 191-199.   

Abstract: A prevalence study was carried out a rural community in Tiruvallur district in Tami Nadu to standardize the method of assessing an X-ray reader in tuberculosis (TB) prevalence surveys by means of different measures of agreement between the reader and a Standard Reader (SR).

The exercise on assessing the X-ray readers was carried out on two occasions; one involving three trainee readers (R ₁ , R ₂ , and R ₃ ), and the other involving one trainee reader (R ₄ ). The extent of agreement was estimated using Kappa statistics (K), over-diagnosis, under-diagnosis, crude agreement and prevalence adjusted bias adjusted kappa (PABAK).

The overall performance of readers R₁ 1 , R ₂ , and R ₃ was not satisfactory in terms of K (21, 34 and 14%) in the first assessment. The K, over-diagnosis and under-diagnosis were estimated to be 61, 28 and 4% for R 1 , 63, 18 and 4% for R 2 and 58, 31 and 5% for R₃ in the final assessment. This suggested that R 2 performed well compared to the other two readers. The K was 68% for R 4 in the first assessment. As the over-diagnosis was to the extent of 40%, the trainee reader underwent one more assessment. The K was 64% which was as good as before, but there was no improvement in the over-diagnosis (43.5%) in the second assessment.

Based on the performance, only one reader (R ₂ ) was certified as qualified for X-ray reading in the first occasion while the reader (R ₄ ) assessed in the second occasion was not qualified. These findings were subject to the inherent variation in the SR's readings against which the readers were assessed.

Keywords: TB, X-ray reader, Standard reader, Agreement, Over- diagnosis, Under-diagnosis.

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