Human chorionic gonadotropin discriminatory zone in ectopic pregnancy: does assay harmonization matter?

Analytical evaluation of the Radiometer AQT90 FLEX βhCG assay

Objectives

Many hospitals cannot afford an hCG assay on a central lab analyzer and turn to point of care testing (POCT) solutions. The Radiometer AQT90 FLEX is a small benchtop immunoareement between the AQT90 and comparator methods for samples with hCG ssay analyzer for use in the laboratory or at the patient bedside. This study evaluated the analytical performance of the AQT90's βhCG assay.

Methods

Precision was assessed using whole blood patient samples and two levels of quality control. Linearity was assessed by dilution of a high hCG plasma sample. Carryover and hook effect were assessed using high and low hCG samples. Method comparisons were done against Abbott i-STAT Total βhCG, Beckman Coulter Total βhCG (5th IS), and Roche hCG+β. Sample concentrations ranged from<2 IU/L to 4,973 IU/L.

Results

Repeatability and within-laboratory precision passed most manufacturer's claims and allowable error criteria. Linearity was validated from<2 IU/L to 4,741 IU/L. Hook effect was not observed up to 2,446,448 IU/L. Carryover was<4.0 ppm. A linear relationship was observed with i-STAT, Beckman and Roche methods. At>20 IU/L, biases were apparent against all three comparator assays (i-STAT: +20%, Roche: +30%, Beckman: +5 to 15%). At ≤20 IU/L, the acceptability of agreement varied according to TAE specifications. Concordance between AQT90 and comparator assays using 5 IU/L as the medical decision level ranged from 69% to 81%.

Conclusions

Overall, the AQT90 hCG assay performed well and would be suitable for smaller suburban or rural hospitals. Some limitations have been noted and should be kept in mind during clinical testing.

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Analytical evaluation of the Radiometer AQT90 FLEX βhCG assay.

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Most of Radiometer's claims and TAE criteria met by the AQT90.

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Clinically significant differences with comparators at high concentrations.

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Clinically insignificant differences with comparators at low concentrations.

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Suitable for use at smaller suburban or rural hospitals for hCG testing.

Comparison of two assays measuring human chorionic gonadotrophin serum concentrations in pregnancy termination and trophoblastic or non-trophoblastic tumours

BACKGROUND

Differences in human chorionic gonadotrophin (hCG) results provided by the commercial immunoassays reflect the heterogeneity of antibodies and the use of suboptimal standards. As a consequence, the principal forms of hCG and metabolites are differentially detected and the hCG tests are not suited for the same clinical applications. Conflicting results are available in the literature regarding which hCG variants are recognized by the Roche Elecsys hCG + β test. The aim of our study was to compare the hCG concentrations provided by the Siemens Immulite 2000 test and the Roche test as well as to assess the concordance between both assays.

METHODS

In this purpose, 152 samples obtained from women and 44 samples from men were analysed by both tests during the follow-up of pregnancy termination, gestational trophoblastic disease and malignancies. The intermediate precision of the Roche test was also investigated on a pool with a low hCG concentration.

RESULTS AND CONCLUSIONS

The hCG concentrations measured with the Roche test were slightly lower compared with the Siemens assay; mean biases of -34.2% and -8% were respectively obtained for hCG values ≤100 UI/L and higher than 100 UI/L. The overall agreement between both assays was 96.1% for women and 97.7% for men. By using an upper reference limit of 3.2 UI/L for women and 1.6 UI/L for men, the Roche test demonstrated a respective concordance of 98.7% and 100%. This test also yielded an excellent precision with a coefficient of variation of 2.8% at a mean hCG concentration of 7 UI/L.

Ratios of biochemical markers in peritoneal fluid to those in venous blood for the diagnosis of ruptured tubal pregnancy: A prospective study

OBJECTIVES

Ectopic pregnancies are among the leading causes of maternal morbidity and mortality in both developed and emerging nations, but tests for early, accurate, and convenient detection are lacking.

STUDY DESIGN

Between January 2013 and February 2015, 504 women with tubal pregnancy were prospectively recruited, and their clinical characteristics were recorded. Samples of peritoneal fluid were collected by culdocentesis, and venous blood was drawn from the antecubital vein. In samples from each source, levels of the following biochemical markers were measured: cancer antigen 125 (CA125), human chorionic gonadotropin (hCG), progesterone, vascular endothelial growth factor, and creatine kinase.

RESULTS

The ratios of biochemical markers in the peritoneal fluid and in the blood (R_p/v) were calculated. The median of R_p/v-CA125 and R_p/v-hCG were significantly lower in the ruptured ectopic pregnancy group than in the unruptured group. The optimal cutoff value to detect ectopic pregnancy rupture was 401.5U/mL as the upper limit for peritoneal CA125, with a sensitivity of 93.5% and specificity of 74.2%. The optimal cutoff value was 18.7 as the upper limit in the peritoneal fluid/blood ratio (R_p/v) of CA125, with a sensitivity of 77.5% and specificity of 68.4%.

CONCLUSIONS

In countries with poor access to laparoscopy, culdocentesis is useful. In this study, culdocentesis provided additional information for management of abdominal pain when laparoscopy is not available. The authors propose R_p/v cutoff values that can be used conveniently and quickly to diagnose ruptured ectopic pregnancies and bleeding, enabling rapid and appropriate therapeutic responses.

Pathology consultation on human chorionic gonadotropin testing for pregnancy assessment

OBJECTIVES

To provide clarity on the use of qualitative and quantitative human chorionic gonadotropin (hCG) tests for the assessment of pregnancy.

METHODS

A case scenario and a brief review of the relevant literature describing clinical and analytical considerations regarding hCG testing are presented.

RESULTS

In pregnancy, hCG is nearly always detectable in serum and urine within 16 days after ovulation. Serial hCG testing is valuable in the evaluation of suspected ectopic pregnancy. hCG assays vary in their analytical specificity, and qualitative tests may be less analytically sensitive than claimed. Erroneous hCG test results can occur for several reasons.

CONCLUSIONS

hCG assays are reliable diagnostic tests for pregnancy assessment, but a clear understanding of their limitations is necessary for appropriate result interpretation.

Ectopic pregnancy secondary to in vitro fertilisation-embryo transfer: pathogenic mechanisms and management strategies

BACKGROUND

Ectopic pregnancy (EP) is the leading cause of maternal morbidity and mortality during the first trimester and the incidence increases dramatically with in vitro fertilisation and embryo transfer (IVF-ET). The co-existence of an EP with a viable intrauterine pregnancy (IUP) is known as heterotopic pregnancy (HP) affecting about 1% of patients during assisted conception. EP/HP can cause significant morbidity and occasional mortality and represent diagnostic and therapeutic challenges, particularly during fertility treatment. Many risk factors related to IVF-ET techniques and the cause of infertility have been documented. The combination of transvaginal ultrasound (TVS) and serum human chorionic gonadotrophin (hCG) is the most reliable diagnostic tool, with early diagnosis of EP/HP permitting conservative management. This review describes the risk factors, diagnostic modalities and treatment approaches of EP/HP during IVF-ET and also their impact on subsequent fertility treatment.

METHODS

The scientific literature was searched for studies investigating EP/HP during IVF-ET. Publications in English and within the past 6 years were mostly selected.

RESULTS

A history of tubal infertility, pelvic inflammatory disease and specific aspects of embryo transfer technique are the most significant risk factors for later EP. Early measurement of serum hCG and performance of TVS by an expert operator as early as gestational week 5 can identify cases of possible EP. These women should be closely monitored with repeated ultrasound and hCG measurement until a diagnosis is reached. Treatment must be customised to the clinical condition and future fertility requirements of the patient. In cases of HP, the viable IUP can be preserved in the majority of cases but requires early detection of HP. No apparent negative impact of the different treatment approaches for EP/HP on subsequent IVF-ET, except for risk of recurrence.

CONCLUSIONS

EP/HP are tragic events in a couple's reproductive life, and the earlier the diagnosis the better the prognosis. Due to the increase incidence following IVF-ET, there is a compelling need to develop a diagnostic biomarker/algorithm that can predict pregnancy outcome with high sensitivity and specificity before IVF-ET to prevent and/or properly manage those who are at higher risk of EP/HP.

Performance characteristics of the Beckman Coulter total βhCG (5th IS) assay

BACKGROUND

Beckman Coulter recently released the first commercially available hCG reagent calibrated against the 5th International Standard (IS) for hCG (total βhCG (5th IS)). We performed a comprehensive analytical validation of this reagent.

METHODS

Precision experiments were completed using 3 concentrations of commercial quality control material. Linearity, sample stability, and analytical sensitivity were evaluated using pools of human serum. Reportable range was assessed by comparing manual dilutions to those performed by the instrument. Male and female reference intervals were established using residual serum specimens submitted for routine testing. Inter-lot variability of hCG assay reagent was assessed by analyzing serum specimens with detectable hCG using 2 different reagent lots. Inter-assay variability was established using 203 serum specimens analyzed for hCG on 6 different reagent platforms.

RESULTS

Inter-day precision showed a CV of <6.0% for all concentrations of QC material. LOB, LOD, and LOQ were determined to be 0.3, 0.4, and 0.6 U/l, respectively. The Access (5th IS) reagent has an average positive bias of approximately 20% when compared to most platforms and the previous generation Beckman hCG assay. Results were consistent between lots. Female reference intervals varied by age: <1.0 U/l (<41 y), <6.0 U/l (41-50 y), and <8.0 U/l (>50 y). Male reference intervals were <2.0 U/l.

CONCLUSIONS

The analytical performance of the total βhCG (5th IS) was established. Care should be taken to re-baseline patients needing serial monitoring and/or notify physicians when transitioning to the total βhCG (5th IS) reagent.