# Coagulation parameter-based nomogram for the diagnosis of obstetric antiphospholipid syndrome and its subtypes

## TL;DR

This study creates a new diagnostic tool for obstetric antiphospholipid syndrome using coagulation parameters to improve detection beyond current criteria.

## Contribution

A novel nomogram is developed to diagnose OAPS and its subtypes using clinical and laboratory parameters.

## Key findings

- The nomogram achieved high accuracy with an area under the curve of 0.97 in the training set and 0.99 in the validation set.
- Key risk factors included antinuclear antibody titer, complement C3, anti-β2 glycoprotein I, and thrombin-antithrombin complex levels.
- The nomogram improved diagnostic sensitivity and specificity for both criteria and non-criteria-defined OAPS.

## Abstract

Currently available classification criteria for obstetric antiphospholipid syndrome (OAPS) are often overly strict and may miss a considerable number of patients with so-called “non-criteria-defined OAPS”. We aimed to establish a diagnostic nomogram based on clinical and laboratory parameters to facilitate the diagnostic efficacy for OAPS by incorporating both criteria – and non-criteria – defined OAPS. We retrospectively analyzed the clinical and laboratory data of 45 patients with criteria-defined OAPS, 57 with non-criteria-defined OAPS, and 80 age-matched healthy controls between September 2023 and March 2024. We established a nomogram for OAPS based on the risk factors identified through logistic regression and evaluated its performance using the receiver-operating characteristic curve, calibration curve, and decision curve analysis. Antinuclear antibody titer, as well as levels of complement C3, anti-β2 glycoprotein I, thrombin-antithrombin complex, and Von Willebrand factor were independent risk factors for OAPS (P < 0.05). In the training set, the nomogram established using these variables exhibited an area under the curve of 0.97, a sensitivity of 89 %, and a specificity of 94 %. In the validation set, these values were 0.99, 100 % and 88 %, respectively. The nomogram demonstrated enhanced diagnostic capabilities and facilitated more precise treatment guidance for OAPS.