Care is needed before single test results are combined

EDITOR—Tonelli et al have provided valuable data for those interested in the interpretation of multiple test results. I differ, however, on the question of the evaluations of interaction and risk “additivity.”1

It seems hard to believe that the interaction between the tests is of only “modest importance” when the odds of death are altered threefold for renal impairment and twofold for proteinuria (by the presence …