Objective: The purpose of this study was to investigate the validity of home pregnancy tests (HPTs) around the time of the missed menses.
Study design: Levels of human chorionic gonadotropin (hCG) were determined in urine around the time of the missed menses, and 5th and 95th centiles were calculated. In a blind study evaluating 18 brands of HPTs, each was tested six times with five concentrations of hCG, 0 to 100 mIU/mL. Sensitivity was defined as the concentration at which six of six brands gave positive results, at the suggested reading time or at an extended time.
Results: It was estimated that a sensitivity of 12.5 mIU/mL was needed to detect 95% of pregnancies at the time of missing menses. Only 1 of 18 HPTs had this sensitivity. If faintly discernible results considered, 2 of 18 brands gave false-positive or invalid results. Clear positive results were given by only 44% of the brands at 100 mIU/mL hCG. If one accepted faintly discernible and extended reading times, all brands responded at 100 mIU/mL. A test with 100 mIU/mL sensitivity would detect approximately 16% of pregnancies at the time of missed menses.
Conclusion: The utility of HPTs is questioned. Clinicians need to be aware of the limitations of current HPT brands.