Robert D. Nerenz

Screening Method to Evaluate Point-of-Care Human Chorionic Gonadotropin (hCG) Devices for Susceptibility to the Hook Effect by hCG β Core Fragment: Evaluation of 11 Devices

BACKGROUND The predominant hCG variant in urine, hCG β core fragment (hCGβcf), has been demonstrated to cause false-negative results in qualitative point-of-care (POC) hCG devices. This is a major concern for healthcare professionals using POC pregnancy tests. We developed a screening method to evaluate qualitative POC hCG devices for their susceptibility to inhibition by hCGβcf. Using this method, we evaluated the performance of 11 commonly used devices. METHODS A wide range of purified hCG and hCGβcf concentrations were mixed and tested on 2 POC devices. By use of those results, a screening method was defined and 9 additional POC devices were evaluated. Two solutions containing (a) 500 pmol/L (171 IU/L) intact hCG with 0 pmol/L hCGβcf and (b) 500 pmol/L intact hCG with 500 000 pmol/L hCGβcf were used to screen all POC devices. RESULTS The OSOM and Cen-Med Elite devices were found to be most susceptible to false-negative results due to hCGβcf. The BC Icon 20 and the Alere were the least susceptible. The remaining 7 were moderately affected. Devices that gave the strongest signal with hCGβcf alone were those that were least likely to show a hook effect. CONCLUSIONS The screening method put forth here can be used by device users and manufacturers to evaluate POC devices for inhibition by hCGβcf. Of 11 devices evaluated, only 2 have been identified that exhibit minimal to no susceptibility to hCGβcf.

Estimating the hCGβcf in urine during pregnancy.

OBJECTIVE Elevated urine concentrations of hCG beta core fragment (hCGβcf) are known to cause false negative qualitative point-of-care hCG test results, but limited information is available regarding urine hCGβcf. In this study, we evaluate the relationship between serum and urine hCG concentrations and the frequency of elevated urine hCGβcf concentrations. DESIGN AND METHODS Paired serum and urine specimens were obtained from 60 women at various stages of pregnancy and hCG was measured using the Abbott Architect and Roche Cobas e602 assays. Urine specimens with the greatest difference in urine hCG concentrations between these two instruments were tested using a qualitative point-of-care device and hCGβcf was quantified using LC-MS/MS. RESULTS Urine hCG concentrations were lower than serum and the magnitude of the difference depended on whether the hCG assay detected hCGβcf. Elevated hCGβcf concentrations (>280,000pmol/L) were observed in 12% of specimens from an unselected patient population. There was a significant correlation (r=0.97; p<0.0001) between the difference (Roche hCG-Abbott hCG) and the hCGβcf concentration as measured by LC-MS/MS (Roche-Abbott difference IU/L=(hCGβcf (pmol/L)∗0.131+656)). CONCLUSIONS A correlation exists between serum and urine hCG concentrations but this correlation is variable. hCGβcf concentrations can be estimated using two automated assay reagent platforms that differ in their recognition of hCGβcf.

Characterizing urinary hCGβcf patterns during pregnancy

OBJECTIVE Elevated concentrations of hCG beta core fragment (hCGβcf) are known to cause false-negative results in qualitative urine pregnancy test devices, but the pattern of urinary hCGβcf during normal pregnancy has not been well characterized. Here, we evaluate the relationship between urine hCG, hCGβcf, and hCG free β subunit (hCGβ) during pregnancy. DESIGN AND METHODS Banked second trimester urine specimens from 100 pregnant women were screened for high concentrations of hCGβcf using a qualitative point-of-care device known to demonstrate false-negative results in the presence of elevated hCGβcf concentrations. Additional first and third trimester specimens from the same pregnancy were obtained from 10 women who generated negative/faint positive results, 5 women who generated intermediate positive results, and 10 women who generated strong positive results on the point-of-care device. Intact hCG, hCGβcf, hCGβ, and specific gravity were quantified in these 75 specimens. RESULTS Urinary hCGβcf concentrations were greater than intact hCG concentrations at all times. A strong correlation (r(2)=0.70) was observed between urine intact hCG and hCGβcf concentrations. A poor correlation was observed between specific gravity and intact hCG (r(2)=0.32), hCGβ (r(2)=0.32), and hCGβcf (r(2)=0.32). The highest hCGβcf concentrations were observed between 10 and 16weeks gestation but individual women demonstrated very different patterns of hCGβcf excretion. CONCLUSIONS Urine specimens with elevated hCGβcf are frequently encountered during pregnancy but hCGβcf excretion patterns are unpredictable. Manufacturers and clinicians must appreciate that hCGβcf is the major immunoreactive component in urine during pregnancy and must design and interpret qualitative urine hCG test results accordingly.

Improved Performance of Point-of-Care Human Chorionic Gonadotropin Pregnancy Device

To the Editor: We have previously described false-negative point-of-care (POC)1 human chorionic gonadotropin (hCG) pregnancy test results caused by high concentrations of hCG β core fragment (hCGβcf) (1, 2). At high concentrations, hCGβcf can saturate the antibodies used in some POC devices, resulting in diminished signal. Importantly, urine hCGβcf concentrations can be increased during normal pregnancy, making the use of such devices dangerous because they may lead to administration of inappropriate treatment (3, 4). Furthermore, it is impossible to predict which women are likely to produce urine with high hCGβcf concentrations and at what point in pregnancy the increased concentrations will be encountered. We previously evaluated 11 POC hCG devices for susceptibility to false-negative findings owing to high hCGβcf (2). Among these, the OSOM hCG Combo device was the most susceptible to false-negative results. Recently, it came to our attention that the manufacturer of the OSOM hCG Combo pregnancy test has 2 new pregnancy tests on its website—the OSOM Card and the OSOM Ultra hCG—in addition to the original OSOM Combo. We were hopeful that the manufacturer had reformulated its devices to avoid false-negative results like other manufacturers have done (5). Here, we have tested all 3 OSOM devices for susceptibility to false-negative findings. We used our previously described screening method …

Inappropriate Off-label Use of a Qualitative, Point-of-care hCG Device Letter With Response

Author(s): Nerenz, Robert D; Gronowski, Ann M; Grenache, David G | Abstract: N/A, letter to the editor

Inappropriate Off-label Use of a Qualitative, Point-of-care hCG Device

Author(s): Nerenz, Robert D; Gronowski, Ann M; Grenache, David G | Abstract: N/A, letter to the editor

What's Wrong with These Pleural Fluid Samples?

A 55-year-old man with a history of pulmonary metastatic disease underwent thoracentesis for evaluation of a pleural effusion. The pH of the pleural fluid sample was measured using an ABL835 blood gas analyzer, which yielded a value of 7.37. As part of new instrument validation, the sample was immediately tested using an ABL90 analyzer, which …

Premenopausal Amenorrhea: What's in a Number?

A 33-year-old nulligravid woman presented to her gynecologist after experiencing 5 months of secondary amenorrhea following discontinuation of oral contraceptives. She had undergone normal puberty and menarche with no significant past medical or surgical history. Her family history was unremarkable other than a brother with developmental delay. On exam she was 165 cm tall and weighed 67 kg, with a body mass index of 24.6 kg/m2 (reference interval, 18.5–24.9 kg/m2). She did not display any evidence of hyperandrogenism (hirsutism or acne), and her pelvic exam was normal. A urine pregnancy test was negative. Initial progestin challenge testing (daily oral administration of 10 mg medroxyprogesterone acetate for 7 days) was negative (no bleeding), indicating that the patient was either hypoestrogenic or that she had a uterine outflow abnormality (e.g., uterine scarring) (1). (Progestin challenge testing provides an indirect assessment of serum estradiol concentrations. Due to false positives and negatives associated with progestin challenge testing, as well as the development of assays directly measuring serum estradiol, progestin challenge tests are not routinely used.) A uterine outflow abnormality was deemed to be unlikely given that the patient had normal menses on oral contraceptive pills and she had no history of uterine manipulation or surgery. Her serum prolactin was 8.3 ng/mL (reference interval, 0.2–24.5 ng/mL), her total testosterone (measured by chemiluminescent immunoassay) was 14 ng/dL (reference interval, 14–76 ng/dL), and her free testosterone (measured by liquid chromatography–tandem mass spectrometry) was 0.2 pg/mL (reference interval, 1.3–9.2 pg/mL). Her serum thyroid-stimulating hormone (TSH)3 was 3.03 μIU/mL (reference interval, 0.36–4.20 μIU/mL) and her follicle-stimulating hormone (FSH) was 57.3 mIU/mL (reference intervals: follicular phase, 2.5–10.2 mIU/mL; midcycle, 3.4–33.4 mIU/mL; luteal phase, 1.5–9.1 mIU/mL; postmenopausal, 23.0–116.3 mIU/mL), confirming a diagnosis of hypergonadotropic hypogonadism. ### QUESTIONS TO CONSIDER 1. What are the causes of oligomenorrhea/amenorrhea in women of childbearing age? 2. What laboratory …