The Standard for Reporting of Diagnostic Accuracy statement promotes the reporting of confidence intervals (CIs) for indices of diagnostic test accuracy. However, these indices must be combined with an estimate of pretest probability to properly interpret the results of such tests, thus yielding positive and negative predictive values. For small sample sizes, CI estimation for predictive values based on the classical logit transformation has been found to be very conservative. A method based on computer simulation has therefore been suggested as an alternative.
ACI procedure for predictive values that yields limits completely contained in those provided by the logit transformation is proposed and evaluated.
The proposed approach to CI construction maintains nominal coverage very well even when sample sizes are small.
Accurate CIs for positive and negative predictive values can be obtained without using computer simulation.
Radon and its decay products have been identified as the second leading cause of lung cancer after tobacco smoking. Thoron is an isotope of radon. With increased awareness of radon, questions related to thoron are arising from the public. Currently, only radon detectors are commonly available to Canadian homeowners. A study on the thoron sensitivities of those radon detectors was undertaken. The average thoron sensitivity relative to radon varied from a factor of 0.012 to 0.74 for the five commonly available types of alpha track radon detectors. The potential impact of thoron sensitivity on radon test results is discussed.