Correction:A multicenter study to improve clinical interpretation of rheumatoid factor and anti-citrullinated protein/peptide antibodies test results

Van Hoovels L, Vander Cruyssen B, Sieghart D, et al. A multicenter study to improve clinical interpretation of rheumatoid factor and anti-citrullinated protein/peptide antibodies test results. RMD Open 2022;8:e002099.

We noticed some errors in the reported 95% confidence intervals (95% CI) of the likelihood ratios of ACPA IgG for rheumatoid arthritis. All 95% CI were verified using the Newcombe-Wilson method.¹ table 4 with the corrected 95% CI of the likelihood ratios is given below.

Table 4. ACPA test result-specific likelihood ratios.

	Interval	Fraction of controls	Fraction of patients	LR	95% CI
Thermo Fisher	< 3.3	0.902	0.299	0.33	0.29–0.39
ACPA	3.3–9.5	0.073	0.065	0.90	0.59–1.38
CO=10 U/mL	9.5–79.8	0.015	0.133	8.93	5.17–15.43
	79.8–324.6	0.007	0.204	27.30	13.32–55.92
	324.6-≥340.0	0.003	0.299	106.90	34.20–334.37
Roche ACPA	< 3.5	0.955	0.362	0.38	0.33–0.43
CO=17 U/mL	3.5–36.1	0.020	0.030	1.54	0.77–3.10
	36.1–230.4	0.015	0.193	12.97	7.67–21.96
	230.4 -≥500.0	0.010	0.415	40.44	22.21–73.64
Svar ACPA	< 4.3	0.898	0.352	0.39	0.34–0.45
CO=25 U/mL	4.3–26.6	0.076	0.035	0.46	0.26–0.80
	26.6–147.8	0.015	0.113	7.58	4.34–13.26
	147.8–398.0	0.007	0.226	30.33	14.85–61.93
	398.0 -≥3200.0	0.003	0.273	97.95	31.29–306.68
IDS ACPA	< 2.0	0.904	0.281	0.31	0.27–0.37
CO=5 AU/mL	2.0–7.7	0.071	0.100	1.41	0.99–2.04
	7.7–43.4	0.015	0.121	8.08	4.65–14.07
	43.4–236.8	0.007	0.273	36.73	18.08–74.62
	236.8 -≥320.0	0.003	0.224	79.98	25.46–251.27
Orgentec	< 5.8	0.900	0.314	0.35	0.30–0.40
ACPA	5.8–14.7	0.075	0.080	1.08	0.73–1.60
CO=20 U/mL	14.7–137.7	0.015	0.156	10.45	6.10–17.88
	137.7–926.0	0.007	0.178	23.93	11.63–49.25
	926.0 -≥1000.0	0.003	0.271	97.06	31.00–303.91
Abbott ACPA	< 1.0	0.913	0.314	0.34	0.30–0.40
CO=5 U/mL	2.7–4.5	0.062	0.063	1.02	0.65–1.60
	4.5–53.1	0.015	0.186	12.47	7.35–21.14
	53.1–188.2	0.007	0.186	24.94	12.13–51.25
	188.2 -≥196.0	0.003	0.251	89.87	28.66–281.74
Euroimmun	< 3.0	0.901	0.319	0.35	0.31–0.41
ACPA	3.0–9.9	0.074	0.070	0.96	0.63–1.45
CO=5 RU/mL	9.9–37.5	0.015	0.106	7.08	4.03–12.44
	37.5–187.7	0.007	0.276	37.07	18.25–75.28
	187.7 -≥200.0	0.003	0.229	81.78	26.04–256.81
BioRad ACPA	< 1.5	0.912	0.334	0.37	0.32–0.43
CO=3 RU/mL	1.5–5.5	0.063	0.077	1.22	0.80–1.88
	5.5–127.5	0.015	0.160	10.63	6.11–18.53
	127.5 -≥300.0	0.010	0.428	42.65	22.76–79.92
Siemens	< 1.1	0.904	0.273	0.30	0.26–0.36
ACPA	1.1–5.6	0.071	0.094	1.32	0.89–1.95
CO=5 U/mL	5.6–57.8	0.015	0.155	10,27	5.89–17.93
	57.8 -≥200.0	0.010	0.478	47.60	25.45–89.02

For RF (table 3), the 95% CI for the likelihood ratio of the Ortho RF interval 16.3–18.7 IU/mL should be 1.03–3.24 instead of 1.07–3.37.