Use of CUSUM and Shewhart charts to monitor regional trends of birth defect reports in New York State

Abstract

The CUSUM method proved useful for identifying changes in birth defect reporting and was able to detect the expected increases in obstructive renal defects. The apparent increase is likely due to improvements in diagnostic imaging techniques. In contrast, we only detected an increase in oral clefts on Long Island, which may be related to under report-ing of cases in the earlier years. CUSUM charts are useful in detecting small, sustained increases in prevalences over time while Shewhart charts are easier to interpret and can detect large sharp increases.