A-167 Repeatedly Positive Serum and Urine Beta-HCG Results in Non-Pregnant Patients—Application of Clinical Decision Support
Authors: Ianosi-Irimie M R , Nikolic D , Bocker Edmonston T 
Published: September 2023

Background

In January of 2020, a 48-year-old woman, status post bilateral tubal ligation was postponed colonoscopy due to a positive urine and serum pregnancy point of care (POC) test. The quantitative serum HCG levels were normal at 4.9 mIU/mL (reference range 0–8 mIU/mL). Follow-up showed that over the prior year there were other 6 similar incidents when nonpregnant patients showed positive qualitative pregnancy results with quantitative HCG levels within “nonpregnancy” normal range being brought to the attention of the laboratory.

Methods

We assessed the possibility of a detection/measurement error including possible interfering antibodies. The likelihood of interfering substances/antibodies that would interact with 2 different types of POC detection systems (urine qualitative—Clinitest HCG Pregnancy test from Siemens Medical Solutions USA, serum qualitative—Pregnancy HCG Rapid Test from Cardinal Health) and serum quantitative—is very low, especially given that both serum and urine specimens were affected, and interfering antibodies are not normally excreted into urine. Testing of the diluted sample showed results like the neat specimen which further excludes interferences in the quantitative reaction as well as a possible hook effect. Based on this we concluded that the results were accurate.Chart review showed that 6 months prior, she had another quantitative HCG test performed using the same instrumentation obtaining a value of 6.6 mIU/mL. At this time a transvaginal ultrasound excluded the presence of any masses or abnormal findings. FSH (47.8 mIU/ml) and LH (49.8 mIU/ml) were found to be within the perimenopausal range. Qualitative serum and urine test were found to be repeatedly positive, while the quantitative tests were within nonpregnancy range, over several months. Retrospective chart review of the other 6 cases revealed similar pattern. Pregnancy, certain tumors (gestational trophoblastic neoplasia, ovarian germ cell tumor), kidney failure and menopause will manifest with increased HCG production. In (peri)menopausal women the pituitary produces HCG up to 14 mIU/mL in association with increased levels of FSH. The qualitative tests were repeatedly positive over several months while the quantitative results remained unchanged, excluding the diagnosis of pregnancy or tumors, and supporting the conclusion that these results are menopause related.

Results

To avoid similar future incidents we added the following comment to the POC test results: “If the result does not fit the clinical picture, please repeat testing on a new sample collected 48–72 h later or order serum HCG quantitative” We also added for the quantitative HCG result, the following comment: “Peri- and postmenopausal patients may have increased HCG of pituitary origin up to 14 mIU/mL. If the result does not fit the clinical picture, FSH measurement can be used for additional information.” During the 12 months preceding the implementation of the comments we had 6 incidents of positive qualitative HCG results in non-pregnant (peri)menopausal patients brought for investigation, and none during the 24 months after that.

Conclusion

The addition of the interpretative comment as clinical decision support increased the efficiency of the medical service, staff engagement and most importantly, patient satisfaction and safety.