To the Editor:--If one believes that preoperative pregnancy testing is a necessity, then "closing the window" as tightly as possible seems mandatory. Available urine test kits detect human chorionic gonadotropin (hCG) levels of 25-50 mIU hCG/ml. Manley et al. [1]tested their patients "within 6 days of the scheduled surgery." hCG concentrations begin to appear 6-7 days after conception at about 10 mIU hCG/ml and double every 1.4-2 days in early pregnancy. [2]Therefore, during a 6-day "window" between testing and surgery, hCG concentrations easily can go from undetectable to detectable (i.e., from 10 to 160 mIU hCG/ml) in the first 2 weeks after conception. It thus seems imperative to perform the test on the day of surgery to identify as many pregnant patients as possible. The test we use at our facility (Abbott TestPack Plus hCG-URINE, Abbott Laboratories, Abbott Park, IL) is performed quickly by our preoperative nurses.

Michael K. Rosenberg, M.D., Medical Director, Sinai Surgery Center, 28500 Orchard Lake Road, Farmington Hills, Michigan 48334.

Manley S, de Kelaita G, Joseph NJ, Salem MR, Heyman HJ: Preoperative pregnancy testing in ambulatory surgery. ANESTHESIOLOGY 1995; 83:690-3.
Cunningham FG, MacDonald PC, Leveno KJ, Grant NF, Gilstrop LC: Williams Obstetrics. Norwalk, Appleton and Lange, 1993, pp 24-8.