Assessing the effect of multiple linkage tests in complex diseases.

The significance of a lod score value of 3 is very difficult to assess in linkage studies between a genetic marker and a complex disease. One reason is that multiple tests may have been performed, voluntarily or otherwise. For the same disease, linkage may be tested by different laboratories with several markers under various genetic models and diagnostic schemes for the disease. In such a case, we show that the probability of getting a lod score value of 3 under independent transmission of the disease and the marker may be not negligible.