ABSTRACT
Human chorionic gonadotropin (hCG) was measured in 117 serum samples with known quantities of hCG after a dilutional modification of a reliable, simple, and inexpensive qualitative assay for hCG. The modification yielded a semiquantitative assay for hCG with a sensitivity of 5000 mIU/mL. At hCG concentrations below 4000 mIU/mL, the assay had no false-negative or false-positive results; above 6500 mIU/mL, there were also no false-negative or false-positive results. In the range of 4000-6500 mIU/mL, the clinical false-positive rate was 28%. Using the described dilutional modification of this qualitative hCG assay, the test is semiquantitative, and is useful in selecting the appropriate time to perform ultrasound and laparoscopy in women suspected of having an ectopic pregnancy.