PGF and rheumatoid arthritis: Importantly, the soluble-fms-like tyrosine kinase-1 (sFlt-1)/placental growth factor (PlGF) ratio, a widely used biomarker for preeclampsia, remains unaffected by RA disease activity or sulfasalazine use, and a threshold value of ≤38 retains its predictive value in this population [80].