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

BACKGROUND: Proactive therapeutic drug monitoring (TDM) is often challenged by long turnaround time when using enzyme-linked immunosorbent assays (ELISAs), especially when analyses are centralised. Point-of-care tests (POCTs) allow rapid assessments, but data on their agreement with existing in-house methodologies are scarce. OBJECTIVE: To examine the agreement between a POCT by ProciseDx (San Diego, CA) and the most frequently used in-house ELISA for infliximab (IFX) quantification in Sweden. METHODS: Serum samples were analysed using the in-house ELISA, Karolinska University Hospital, Stockholm, Sweden and a POCT by ProciseDx (San Diego, CA). Agreement was assessed and differences were examined. RESULTS: Samples from 61 inflammatory bowel disease (IBD) patients were analysed with a median IFX concentration of 7.9 µg/mL (interquartile range (IQR) 5.5-13) for the POCT and 7.9 µg/mL (IQR 5.2-12) for the ELISA (Pearson's correlation coefficient = 0.95 (95% CI 0.92-0.97, p < .01)). A Passing-Bablok regression yielded an intercept of -0.44 and a slope of 1.09. The Bland-Altman plot showed a systemic bias of -0.77 µg/mL (95% CI -0.18 to -1.4) between the methods. The upper limit of agreement was 3.7 (95% CI 2.7-4.8) (µg/mL), whereas the lower limit agreement was -5.3 (95% CI -6.3 to -4.3) (µg/mL). An excellent reliability was observed, intraclass correlation showed = 0.94 (95% CI 0.89-0.96, p < .0001). When defining IFX concentration as subtherapeutic (<3.0 µg/mL), therapeutic (3.0-7.0 µg/mL) or supratherapeutic (>7.0 µg/mL) drug levels, Kappa statistics showed a substantial agreement (0.79). CONCLUSIONS: The POCT by ProciseDx (San Diego, CA) demonstrated a good agreement with the in-house ELISA, supporting its use for rapid IFX quantification.

Ustekinumab treatment in ulcerative colitis: Real-world data from the Swedish inflammatory bowel disease quality register.

BACKGROUND: Real-world data on clinical outcomes of ustekinumab in ulcerative colitis are lacking. OBJECTIVE: To assess short- and long-term clinical outcomes of ustekinumab in ulcerative colitis. METHODS: Adult ulcerative colitis patients without previous colectomy starting ustekinumab treatment up until 11 December 2020 were identified through the Swedish Inflammatory Bowel Disease Register (SWIBREG). Prospectively recorded data were extracted from the SWIBREG. The primary outcome was persistence to ustekinumab 16 weeks after treatment initiation. Secondary outcomes included drug persistence beyond week 16, clinical remission (defined as a patient-reported Mayo rectal bleeding subscore = 0 and stool frequency subscore ≤1), biochemical remission (defined as faecal-calprotectin <250 µg/g) and changes in health-related quality of life (HRQoL), as measured by the Short Health Scale (SHS). Logistic regression was used to identify potential predictors of ustekinumab persistence at 16 weeks. RESULTS: Of the 133 patients with ulcerative colitis, only three were naïve to biologics and tofacitinib. The persistence rates of ustekinumab were 115/133 (86%) at 16 weeks and 89/133 (67%) at last follow-up, that is, after a median follow-up of 32 (interquartile range 19-56) weeks. The clinical remission rates were 17% at 16 weeks and 32% at the last follow-up. The corresponding rates for biochemical remission were 14% and 23%. The median faecal-calprotectin concentration decreased from 740 µg/g at baseline to 98 µg/g at the last follow-up (p < 0.01, n = 37). Improvement was seen in each dimension of the SHS between baseline and last follow-up (p < 0.01 for each dimension, n = 46). Male sex was associated with ustekinumab persistence at 16 weeks (adjusted odds ratio = 4.00, 95% confidence interval: 1.35-11.83). CONCLUSION: In this nationwide real-world cohort of ulcerative colitis patients with prior drug failures, including other biologics and tofacitinib, ustekinumab was associated with high drug persistence rates and improvements in clinical, biochemical and HRQoL measures.