Strong Ion Difference: A Promising Biomarker for Differential Diagnosis of Hypertensive Disorders in Pregnancy

Abstract

Aim: Hypertensive disorders of pregnancy (HDP), including gestational hypertension (GHT) and preeclampsia, are significant causes of maternal and neonatal morbidity. Early differentiation is crucial, especially in severe cases. This study evaluated venous blood gas parameters, specifically Strong Ion Difference (SID) and Apparent Strong Ion Difference (SIDa), to distinguish GHT from preeclampsia and severe preeclampsia. Material and Method: This retrospective, single-center study analyzed 94 pregnant patients with hypertension of unknown origin beyond 20 weeks’ gestation (October 2021–2022). Patients were categorized as GHT (n=39) or preeclampsia spectrum (n=55), with subgroup analysis in 74 patients without chronic diseases. Proteinuria was assessed via 24-hour urine collection or protein/ creatinine ratio. Statistical methods included t-tests, chi-square, Mann-Whitney U, Kappa, and ROC analysis. Results: Significant differences were found between GHT and preeclampsia groups in dipstick protein ≥2+, protein/creatinine ratio, SID, and SIDa (p<0.001). In the subgroup analysis, significant differences were noted for dipstick protein ≥1+ and ≥2+, protein/creatinine ratio, SID, and SIDa (p=0.001, p<0.001, p<0.001, p=0.015, p=0.012). Kappa analysis showed poor agreement between SID and proteinuria in the total cohort (κ=-0.166, p=0.092) and slight agreement in the subgroup analysis (κ=0.190, p=0.020), suggesting a weak concordance between these two parameters. SID showed moderate discriminatory power (AUC: 0.672 overall, 0.668 in the subgroup). Conclusion: SID and SIDa are promising biomarkers for distinguishing GHT from preeclampsia. Further extensive cohort studies are needed to establish accurate cut-off values for routine clinical use.

Keywords

• gestational hypertension
• preeclampsia
• severe preeclampsia
• SID
• strong ion difference

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