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Surely this depends on the sensitivity of the urine test used. We use urine strips from Guest which have a sensitivity of 25 iu/L usually capable of confirming pregnancy by the first day of missed menstrual period. We try to discourage a serum (sensitive) test as a first line screen for pregnancy. We use Bayer immuno 1 which has different calibration ranges for HCG as a tumour marker and Pregnancy related HCG. At one stage we tended to run any ?Pregnant samples that came out as <100 iu/L on the pregnancy related range again on the tumour marker calibrated assay. This was not cost effective or indeed useful. We never actually turned up a single pregnancy by this method where the urine strip was negative. John OConnor Eastbourne Hospitals NHS Trust ----- Original Message ----- From: Stephen Davis <[log in to unmask]> To: <[log in to unmask]> Sent: 29 October 1999 10:45 Subject: HCG testing - urine v serum > We recently encountered a case where a lady admitted for sterilisation had a negative urine pregnancy test and underwent sterilisation. She was subsequently shown to be pregnant with dates consistent with conception occurring prior to the procedure. > > Should a sensitive serum test have been used rather than a urine test? Does anyone know of cases where laboratories/hospitals have been criticised for using urine test rather than serum in such circumstances? > > > Steve Davis > Principal Biochemist > Department of Clinical Biochemistry > East Glamorgan General Hospital > Church Village > PONTYPRIDD > Mid Glamorgan > CF38 1AB > > %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%