Bias and `Overcall' in Interpreting Chest Radiographs in Young Febrile Children

Few studies have examined the diagnostic validity of the examining physician's interpretation of chest radiographs in young febrile children, and none (to our knowledge) the extent to which the "official" (ie, the radiologist's) reading may be biased by access to the examining physician's reading and to other clinical information. The authors studied 287 consecutive chest radiographs obtained in 286 febrile children 3 to 24 months of age without chronic cardiopulmonary disease or known asthma who presented to a children's hospital emergency department between March 1989 and August 1990. The readings by treating pediatricians, official pediatric radiologists, and a "blind" pediatric radiologist were compared. Official radiologists had access to the treating pediatricians' readings and the clinical information provided on the radiography requisition. The blind radiologist knew only that each child was 3 to 24 months of age and febrile, and he was asked to judge the presence or absence of pneumonia. Using the blind radiologist's reading as the "gold standard" for judging validity of the treating physicians' and official radiologists' readings, sensitivity (.677 vs .647), specificity (.828 vs .849), positive predictive value (PPV, .537 vs .571), and kappa index (κ, .462 vs .475) were quite similar. By contrast, agreement by the treating physicians was considerably higher with the official radiologists' readings as gold standard: sensitivity = .756, specificity = .922, PPV = .795, and κ = .688. When the treating physician's reading was positive, the official radiologists' positivity rate was much higher than the blind radiologist's (74.4% vs 51.8%, P < .005), sensitivity was high (.884) but specificity was low (.436), PPV was .663, and κ was .326. When the treating physicians' reading was negative, however, the pattern was reversed: positivity = 8.5% vs 12.8% (P not significant), sensitivity = .240, specificity = .937, PPV = .353, and κ = .205. Surprisingly, none of the three sets of readings appeared to be influenced by the reporting of clinical signs and symptoms on the radiography requisition. These results indicate that official radiologists are strongly biased by the treating physician's reading. Since such a bias can lead to unnecessary antibiotic treatment and hospital admission, strategies to reduce it should receive high priority.