IgG4:IgG RNA ratio differentiates active disease from remission in granulomatosis with polyangiitis: a new disease activity marker? A cross-sectional and longitudinal study

Table 2 Test characteristics of the different available tests detecting disease activity in our granulomatosis with polyangiitis cohort, using Birmingham Vasculitis Activity Score version 3 as gold standard, with Birmingham Vasculitis Activity Score ≥ 3 reflecting active disease

	ESR	CRP	ANCA titer	Physician VAS	qPCR test
Sensitivity (%)	50	92	73	80	86
Specificity (%)	100	69	38	90	100
Positive predictive value (%)	100	73	52	86	100
Negative predictive value (%)	77	90	60	86	91

Abbreviations: ANCA Antineutrophil cytoplasmic antibodies, CRP C-reactive protein, ESR Erythrocyte sedimentation rate, VAS Visual analogue scale
The cutoff values used were 30 mm/h for ESR, 5 mg/L for CRP, 7 kIU/L for ANCA, 2 or higher for physician VAS, and 11.2% for the qPCR test

ISSN: 1478-6362