Effect of Misdiagnosis
The problem of misdiagnosis or misclassification of a specific disease is another concern of applying capture-recapture methods in the disease surveillance. There are two types of misdiagnoses; false positive diagnosis which erroneously classifies healthy individuals as diseased or falsely identified individuals with disease other than the disease of interest and false negative diagnosis which leaves cases undetected. For most of the disease surveillance system disease misdiagnosis is not a serious problem. However, for certain types of diseases misclassification does occur often. For example the misclassification of colon cancer with rectum cancer. If the surveillance involves mortality statistics, death certificate, the most used source, is often to be found imprecise in classifying the cause of death, with a tendency toward over reporting unspecific diseases (1). According to Brenner H (2), the false-positive and false-negative diagnoses affect differently in the capture-recapture analyses. In a 2-sample method, if both appear and they are balanced, the capture-recapture result is unaffected by the misdiagnoses. However, if false-negative diagnosis is preponderant, it will lead to the underestimation of the total number of cases; while preponderancy of false-positive diagnosis will result in overestimation of the cases. To minimize the problem caused by misdiagnosis, one may consider to combine diagnoses between which misclassification is common (3) or employ the correction procedure provided by Brenner H (2).
1. Sirken MG, Rosenberg HM, Chevarley FM, Curtin LR. The quality of cause-of-death statistics. Am J Public Health 1987;7:137-139.
2. Brenner H. Effects of misdiagnoses on disease monitoring with capture-recapture methods. J Clin Epidemiol 1996;11:1303-1307.
3. Robles SC, Marrett LD, Clarke EA, Risch HA. An application of capture-recapture methods to the estimation of completeness of cancer registration. J Clin Epidemiol 1988;41:495-501.