Pregnancy Testing (Serum hCG)

Purpose:
The Programme aims to assess the performance of organisations measuring Urine and Serum/ whole blood human chorionic gonadotrophin (hCG) for confirmation of pregnancy (classical high sensitivity test) and for professional healthcare providers using low sensitivity or multilevel rapid tests to exclude ongoing pregnancy after medical abortion treatment.

Scope:
The Pregnancy Testing programme is a bimonthly programme available to both PoCT and Laboratory sites. The Programme includes for the assessment of testing using high sensitivity methods for hCG in Pregnancy in Urine and Serum / whole blood and for low sensitivity methods used in the assessment of medical abortion outcome.

Urine Pregnancy Programme
Three samples of liquid human urine covering an appropriate physiological range are distributed bimonthly. Fresh filtered human urine from pregnant and non-pregnant volunteers is used, with additional female human urine spiked with Human Chorionic Gonadotrophin to increase the pathological range. The standard volume is 1mL aliquots, however this can be increased and dispensed into wide neck tubes to those participants using wick-based assay systems. Participants can submit both quantitative and qualitative results.

Serum HCG Programme
Three serum samples spiked with hCG are distributed bimonthly, participants can submit quantitative and qualitative results.

Performance Assessment: The programme is designed to assess both laboratory and method performance, including, sensitivity, interferences, bias, within and between batch imprecision and antigen excess.

Interpretation of the qualitative results is based on the intended purpose of the test and the analysed quantitative target value and / or spiked concentration. For classical pregnancy testing in urine, sensitivities of kits can vary, with quoted limits of detection of 10, 20 or 25 IU/L. A sample is therefore regarded negative at a concentration less than 20 IU/L (equivocal results may be produced at a concentration range of 10-20 IU/L and therefore no penalty is given for returning a positive or weak positive result in this equivocal range.) A sample is regarded positive at a concentration ≥20 IU/L.

For serum hCG, the upper limit reference range is approximately 8 IU/L for non-pregnant pre-menopausal females. Sensitivities of kits vary, however most quote a limit of detection between 10 – 20 IU/L. For interpretation purposes, a sample is regarded negative at a concentration less than 10 IU/L and positive at a concentration ≥10 IU/L.

For the determination of an ongoing pregnancy after medical abortion, a hCG of ≥1000 IU/L is regarded as positive.

The scores broadly reflect clinical importance. A correct result (in agreement with interpretive comment) is given a score of 0. A sliding scale score of between 1and 5 is assigned for incorrectly identified results, where 5 represents a gross misclassification of the result. A negative result for a positive sample is given a score of 3 to 5 depending on the concentration of the positive sample. A positive result for a negative sample is given a score of 2 or 3.

Equivocal comments (for further investigation) for a positive sample are given a score of 1 to 3 depending on the concentration of the positive sample. An equivocal comment (for further investigation) for a negative sample is given a score of 1.

The sensitivities of the methods, the intended purpose of the kits, whether “rule in” or “rule out” are also considered in the scoring. In general, a missed positive sample is given a larger penalty than a misclassified negative as this could lead to missed diagnosis or inappropriate treatment whilst an incorrect negative tends to lead to less severe clinical consequences such as inappropriate further investigation.

Key Features:

Suitable for qualitative and quantitative assays.
Suitable for urine and serum/ whole blood hCG methods.
Suitable for manual or automated lateral flow methods.
Suitable for classical pregnancy testing or determination of outcome after ToP.
Increased volume dispensed into wide neck tubes available for those using lateral flow dip stick assays.
Challenging samples at or near lower limits of detection/ Ag excess to assess sensitivity and Hook effect.
Programme assess both laboratory and method performance, including, sensitivity, interferences, bias, within and between batch imprecision.