HANOVER, NH As people consider the merits or drawbacks of cancer screening, a Dartmouth Medical School study weighs in with some new observations, based on a statistical analysis of past trials, that may help put cancer screening in better perspective.
The conventional way deaths were classified may have caused misclassifications that biased study results in favor of screening, Dartmouth researchers demonstrated. They suggest an additional method of tallying all deaths to help avoid the misinterpretations that can lead investigators to overestimate or underestimate the value of cancer screening.
The findings are reported in the Feb. 6 issue of the Journal of the National Cancer Institute by Dartmouth Medical School professors William C. Black, MD, of radiology and of community and family medicine, and H. Gilbert Welch, MD, of medicine and of community and family medicine, and former medical resident David Haggstrom, MD.
Classifying the cause of death by specific disease is the most widely accepted procedure in randomized trials that assess cancer screening. However, two biasessticky-diagnosis bias and slippery-linkage biasaffect such classification and can alter the assessment of screening value, the researchers found.
The validity of disease-specific mortality assumes that the cause of death can be accurately determined. An alternative end point, all-cause mortality, depends only on an accurate determination of deaths and when they occur; therefore it is unaffected by misclassifications in the cause of death.
People making decisions about screening want to have pertinent information about what it means for them, explained Black, a member of a national expert panel that assesses cancer evidence. He uses the shark analogy popular among his peers. Instructions and aids to protect yourself from a shark attack are meaningless if you dont go in the water.
Similarly, people have to understand how likely they are to be at ris
'"/>
Contact: Hali Wickner
dms.communications@dartmouth.edu
603-650-1492
Dartmouth Medical School
5-Feb-2002