Anti‐BP180 IgG antibody ELISA values correlate with adverse pregnancy outcomes in pemphigoid gestationis

Background Adverse pregnancy outcomes (APO) occur in 35% of patients with pemphigoid gestationis (PG). No biological predictor of APO has been established yet. Objectives To assess a potential relationship between the occurrence of APO and the serum value of anti‐BP180 antibodies at the time of PG diagnosis. Methods Multicentre retrospective study conducted from January 2009 to December 2019 in 35 secondary and tertiary care centres. Inclusion criteria: (i) diagnosis of PG according to clinical, histological and immunological criteria, (ii) ELISA measurement of anti‐BP180 IgG antibodies determined at the time of PG diagnosis with the same commercial kit and (iii) obstetrical data available. Results Of the 95 patients with PG included, 42 had one or more APO, which mainly corresponded to preterm birth (n = 26), intrauterine growth restriction (IUGR) (n = 18) and small weight for gestational age at birth (n = 16). From a ROC curve, we identified a threshold of 150 IU ELISA value as the most discriminating to differentiate between patients with or without IUGR, with 78% sensitivity, 55% specificity, 30% positive and 91% negative predictive value. The threshold >150 IU was confirmed using a cross‐validation based on bootstrap resampling, which showed that the median threshold was 159 IU. Upon adjusting for oral corticosteroid intake and main clinical predictors of APO, an ELISA value of >150 IU was associated with the occurrence of IUGR (OR = 5.11; 95% CI: 1.48–22.30; p = 0.016) but not with any other APO. The combination of blisters and ELISA values higher than 150 IU led to a 2.4‐fold higher risk of all‐cause APO (OR: 10.90; 95% CI: 2.33–82.3) relative to patients with blisters but lower values of anti‐BP180 antibodies (OR of 4.54; 95% CI 0.92–34.2). Conclusion These findings suggest that anti‐BP180 antibody ELISA value in combination with clinical markers is helpful in managing the risk of APO, in particular IUGR, in patients with PG.