Evaluation of ADAM-12 as a Diagnostic Biomarker of Ectopic Pregnancy in Women with a Pregnancy of Unknown Location

BACKGROUND Ectopic pregnancy (EP) remains the most life-threatening acute condition in modern gynaecology. It remains difficult to diagnose early and accurately. Women often present at emergency departments in early pregnancy with a 'pregnancy of unknown location' (PUL) and diagnosis/exclusion of EP is challenging due to a lack of reliable biomarkers. Recent studies suggest that serum levels of a disintegrin and metalloprotease protein-12 (ADAM-12) can be used differentiate EP from viable intrauterine pregnancy (VIUP). Here we describe a prospective study evaluating the performance of ADAM-12 in differentiating EP from the full spectrum of alternative PUL outcomes in an independent patient cohort. METHODOLOGY/PRINCIPAL FINDINGS Sera were collected from 120 patients at their first clinical presentation with a PUL and assayed for ADAM-12 by ELISA. Patients were categorized according to final pregnancy outcomes. Serum ADAM-12 concentrations were increased in women with histologically-confirmed EP (median 442 pg/mL; 25%-75% percentile 232-783 pg/mL) compared to women with VIUP (256 pg/mL; 168-442 pg/mL) or miscarriage (192 pg/mL; 133-476 pg/mL). Serum ADAM-12 did not differentiate histologically-confirmed EP from spontaneously resolving PUL (srPUL) (416 pg/mL; 154-608 pg/mL). The diagnostic potential of ADAM-12 was only significant when 'ambiguous' PUL outcomes were excluded from the analysis (AROC = 0.6633; P = 0.03901). CONCLUSIONS/SIGNIFICANCE When measured in isolation, ADAM-12 levels had limited value as a diagnostic biomarker for EP in our patient cohort. The development of a reliable serum biomarker-based test for EP remains an ongoing challenge.