Sunday, March 21, 2004

CDC Study Discounts Link Between Claritin and Birth Defects

Various news outlets (e.g., the Atlanta Journal-Constitution, CNN, HealthDay) are reporting on a CDC-sponsored study tending to discredit any strong association between mothers' ingestion of loratadine (Claritin) during pregnancy and the birth defect in male children known as hypospadias. An earlier Swedish study had suggested that the risk of hypospadias roughly doubled when pregnant mothers took the drug. A summary of the new CDC study is posted in the CDC's current Morbidity and Mortality Weekly Report.

Is this a clean bill of health for Claritin? The media are having some trouble getting that question straight. (If lawyers are often frustrated over mistakes in press coverage of their cases, imagine how epidemiologists must feel about reportage on their own discipline.) CNN portrays the study's findings as negating a causal association. But that statement apparently goes too far. The Atlanta Journal-Constitution quotes a CDC epidemiologist who says that although the new CDC study would have captured a threefold increase in incidence, there is a 34% statistical chance that it would miss the twofold increase found in the Swedish study. And HealthDay quotes a spokesman for Schering-Plough, which makes Claritin, who advances only the fairly modest claim that the CDC study "confirms the favorable risk-benefit ratio of loratadine."
Fed. R. Evid. 702: If scientific, technical, or other specialized knowledge will assist the trier of fact to understand the evidence or to determine a fact in issue, a witness qualified as an expert by knowledge, skill, experience, training, or education, may testify thereto in the form of an opinion or otherwise, if (1) the testimony is based upon sufficient facts or data, (2) the testimony is the product of reliable principles and methods, and (3) the witness has applied the principles and methods reliably to the facts of the case.