Comparative study of a point-of-care test and an enzyme-linked immunosorbent assay (ELISA) for infliximab levels

Figures & data

Table 1. Demographics and clinical characteristics of patients with inflammatory bowel disease receiving infliximab treatment (n = 61).

	Crohn’s disease (n = 35)	Ulcerative colitis (n = 26)
Male sex, n (%)	23 (66)	12 (46)
Median age, years (IQR)	35 (29–49)	42 (33–52)
Mean BMI, kg/m^2 (SD)	26 (3.4)	27 (3.7)
Smoking status (or vaper), n (%)
Current smoker	3 (9)	4 (15)
Ex-smoker	13 (37)	8 (31)
Never smoker	19 (54)	14 (54)
Disease location, n (%)
Ileal, L1	5 (14)
Colonic, L2	16 (46)
Ileocolonic, L3	13 (37)
Isolated upper disease, L4	1 (3)
Disease behaviour, n (%)
Inflammatory, B1	28 (80)
Stricturing, B2	7 (20)
Penetrating, B3	0 (0)
Perianal disease modifier, p	7 (20)
Disease extent, n (%)
Proctitis, E1		0 (0)
Left-sided colitis, E2		11 (42)
Extensive colitis, E3		13 (50)
Unknown extent		2 (8)
Median PRO2, score	4 (2–10)
Median SCCAI bowel frequency per day, score (IQR)		0 (0–0)
Median SCCAI bowel frequency per night, score (IQR)		0 (0–0)
Median Mayo rectal bleeding subscore, score (IQR)		0 (0–0)
Concurrent IBD medication, n (%)
Corticosteroids	0 (0)	1 (4)
5-Aminosalicylic acid	0 (0)	10 (38)
Immunomodulators	21 (60)	14 (54)

IQR: interquartile range; BMI: body mass index; SD: standard deviation; PRO2: two-item patient reported score derived from Crohn’s Disease Activity Index; SCCAI: Simple Clinical Colitis Activity Index; IBD: inflammatory bowel disease; immunomodulators: azathioprine, 6-mercaptopurine and methotrexate.

Figure 1. Passing–Bablok regression (blue line) with 95% confidence interval (light blue) on infliximab concentrations between the point-of-care test (POCT) based on fluorescence resonance energy transfer (FRET) and an in-house enzyme-linked immunosorbent assay (ELISA). Identity line in black.

Figure 2. Bland–Altman plot on infliximab concentration between conventional in-house ELISA and point-of-care test device with bias (red line) and limits of agreement (dashed red lines).

Data availability statement

No additional data are available due to the Swedish data protection regulation.