Evaluation of serum calponin-2 in the differential diagnosis of pregnancy of unknown location: A prospective analysis.

Abstract

Objective: This study evaluates the diagnostic utility of serum calponin-2 (CNN-2) levels in the differential diagnosis and risk stratification of pregnancy of unknown location (PUL).

Methods: This prospective longitudinal study included 116 patients diagnosed with PUL between September 2022 and September 2023 at a tertiary hospital. Patients were classified according to final diagnosis into ectopic pregnancy (n = 26), failed PUL (n = 36), and intrauterine pregnancy (n = 54) groups and risk stratified into high-risk and low-risk categories using the M6 model. Serum CNN-2 levels were measured at admission. The diagnostic performance of CNN-2 was assessed using receiver operating characteristic curve analysis.

Results: Calponin-2 levels were significantly higher in ectopic pregnancy cases compared to failed PUL and intrauterine pregnancies (P = 0.019 and P < 0.001, respectively) and higher in failed PUL compared to intrauterine pregnancies (P < 0.001). No difference was observed between viable and non-viable intrauterine pregnancies (P = 0.187). CNN-2 distinguished high-risk from low-risk PUL with 88.5% sensitivity and 78.9% specificity at a cut-off of 0.17 ng/mL (AUC = 0.893, P < 0.001). A CNN-2 level of ≤0.15 ng/mL identified intrauterine pregnancies with 90.7% sensitivity and 79% specificity (AUC = 0.904, P < 0.001).

Conclusion: Serum CNN-2 is a promising biomarker for early risk stratification and differential diagnosis in PUL. Its measurement might aid in timely identification of ectopic pregnancies and reduce reliance on serial β-hCG testing. Further multicenter studies are needed to validate its clinical applicability.