Table 5.

Positive predictive values of first-time rheumatoid arthritis diagnoses according to serological subtypes registered in the Danish National Patient Registry in the period 1977–2016 among the participants in the Danish Diet, Cancer, and Health cohort and derived from the Central Denmark Region hospitals by calendar periods

First-time diagnosis in the Danish National Patient Registry, ICD-10 codes	Rheumatoid arthritisa			Rheumatoid arthritis + sDMARDb
	Confirmed rheumatoid arthritis, n	Registered rheumatoid arthritis, n	Positive predictive value % (95% CI)	Confirmed rheumatoid arthritis, n	Registered rheumatoid arthritis, n	Positive predictive value % (95% CI)
M05 – seropositive rheumatoid arthritis
1988–2010	71	115	61.7 (52.4–70.3)	68	84	81.0 (70.9–88.1)
2011–2016	22	35	62.9 (45.1–77.7)	21	27	77.8 (57.0–90.2)
M06 – other rheumatoid arthritis
1988–2010	18	99	18.2 (11.7–27.2)	13	50	26.0 (15.4–40.3)
2011–2016	18	45	40.0 (26.4–55.4)	17	23	73.9 (50.9–88.6)

Notes:

^aPatients with the first-time ever rheumatoid arthritis diagnosis registration in the Danish National Patient Registry;

^bpatients with the first-time ever rheumatoid arthritis diagnosis registration in the Danish National Patient Registry who subsequently, at least once, redeemed a prescription for a sDMARD.

Abbreviations: ICD, International Classification of Diseases; sDMARD, synthetic disease-modifying antirheumatic drug.