Retrospective evaluation of 99th percentile hCG results to adjust clinical decision points.

While accurate measurement of chorionic gonadotropin (hCG) is necessary, so are appropriate clinical decision points (CDPs) for patients of all ages. The CDP for hCG is intended to identify early pregnancy in patients of child bearing age; non-pregnant patients who are older frequently yield hCG results > 5 IU/L, making the use of a low hCG CDP problematic for these patients. Using a retrospective review of all hCG results generated over a 32-month period, 8507 hCG results from non-pregnant females of all ages were analyzed. Patients < 40 years of age comprised 74% of hCG measurements, and produced hCG results ≥ 5 IU/L 1% of the time, but this frequency increased in patients 40-49 (17% of hCG results; 4% ≥5 IU/L) and ≥50 (9% of hCG results; 20% ≥ 5 IU/L). While only 3% of hCG results were ≥5 IU/L in the overall data set, all (24/24) of hCG results 10-14 IU/L came from patients ≥ 40 years of age and all (3/3) hCG results ≥ 15 IU/L came from patients ≥ 50 years of age. The 99th percentile hCG results in the population were 3 IU/L in patients < 40, 7 IU/L in patients 40-49, and 13 IU/L in patients ≥ 50 years of age. These findings demonstrate a progressive increase in measurable hCG correlating to patient age and demonstrate a proof-of-concept that institutions could assess 99th percentile hCG results to assign more appropriate method-dependent CDPs to different age groups.