Is there an added value of faecal calprotectin and haemoglobin in the diagnostic work-up for primary care patients suspected of significant colorectal disease? A cross-sectional diagnostic study

Table 2 Improvement in discrimination, reclassification, and explained variation upon various extensions of the basic diagnostic model and individual faecal biomarker extended models for SCD, as observed in 810 Dutch patients with lower abdominal complaints referred for endoscopy in the CEDAR study

	Absolute change in AUC		NRI^c		IDI		Relative IDI, %	Absolute change in R², %^d
Diagnostic model	Estimate (95 % CI)	P value^b	Estimate (95 % CI)	P value	Estimate (95 % CI)	P value	Relative IDI, %	Absolute change in R², %^d
Basic diagnostic model (AUC: 0.741; 95 % CI, 0.694–0.789)^a
+ Calprotectin POC test	0.022 (0.00–0.05)	0.078	0.15 (0.07–0.24)	<0.001	0.04 (0.02–0.06)	<0.001	27.6	4.5
+ Calprotectin ELISA test	0.019 (0.00–0.04)	0.11	0.13 (0.04–0.22)	0.005	0.04 (0.01–0.06)	0.005	27.5	4.3
+ POC FIT	0.090 (0.06–0.12)	<0.001	0.38 (0.24–0.51)	<0.001	0.13 (0.09–0.16)	<0.001	91.0	15.4
+ POC FIT and calprotectin POC test	0.096 (0.07–0.12)	<0.001	0.38 (0.25–0.51)	<0.001	0.14 (0.10–0.18)	<0.001	100.0	16.7
+ POC FIT and calprotectin ELISA test	0.096 (0.07–0.12)	<0.001	0.40 (0.27–0.52)	<0.001	0.14 (0.10–0.18)	<0.001	100.7	16.8
Calprotectin POC test extended model (AUC: 0.763; 95 % CI, 0.718–0.809)
+ POC FIT	0.074 (0.05–0.10)	<0.001	0.23 (0.11–0.35)	<0.001	0.10 (0.07–0.13)	<0.001	56.9	12.3
Calprotectin ELISA test extended model (AUC: 0.760; 95 % CI, 0.714–0.806)
+ POC FIT	0.077 (0.05–0.10)	<0.001	0.26 (0.14–0.39)	<0.001	0.10 (0.07–0.13)	<0.001	57.5	12.4
POC FIT extended model (AUC: 0.831; 95 % CI, 0.791–0.872)
+ Calprotectin POC test	0.006 (0.00–0.02)	0.20	0.01 (–0.06 to 0.07)	0.87	0.01 (0.00–0.03)	0.055	4.7	1.3
+ Calprotectin ELISA test	0.005 (0.00–0.01)	0.20	0.02 (–0.05 to 0.09)	0.59	0.01 (0.00–0.03)	0.064	5.0	1.3

AUC area under the receiver operating characteristic curve; CEDAR Cost-Effectiveness of a Decision rule for Abdominal complaints in primary caRe; CI confidence interval; CRP C-reactive protein; ELISA enzyme-linked immunosorbent assay; FIT faecal immunochemical test for haemoglobin; IDI integrative discrimination improvement; NRI net reclassification improvement; POC point-of-care; SCD significant colorectal disease
^aThe basic diagnostic model consisted of: Age, per 5 years (OR: 1.2 (95 % CI, 1.1–1.3); P < 0.001); Abdominal pain (0.6 (0.4–0.9); P = 0.02); Rectal blood loss (3.1 (2.0–4.8); P < 0.001); Rectal mucus (1.8 (1.2–2.7); P = 0.007); Weight loss (1.5 (1.0–2.5); P = 0.08); Change in bowel habit (1.4 (0.8–2.2); P = 0.23); Abdominal bloating (0.6 (0.4–1.0); P = 0.04); Constipation (0.7 (0.5–1.1); P = 0.12); Abnormal digital rectal examination (1.7 (0.8–3.9); P = 0.20); CRP in mg/L, per log(CRP + 1) (1.3 (1.0–1.6); P = 0.03); CRP was included in the basic model, but omitted from the faecal biomarker extended models as it lost statistical significance (Additional file 1)
^bP value based on 2000-fold bootstrap resampling
^cNRI is the NRI categorical with 5.0 % threshold for low and 50.0 % for high significant colorectal disease risk
^dNagelkerke’s R²

ISSN: 1741-7015