Source: [Klaus Theede on research.regionh.dk](https://research.regionh.dk/da/persons/klaus-theede/)
Authors: Bionoia editorial
Venue: Feature · 2026
Abstract
A Danish gastroenterologist whose decade-long focus on biomarkers, endoscopy, and smarter drug combinations is reshaping how clinicians monitor bowel disease.
Who is Klaus Theede?
Klaus Theede is a gastroenterologist and clinical researcher at Amager og Hvidovre Hospital in Copenhagen, where he works within the Gastro-medicinsk Afdeling. Trained as both a clinician and a scientist — he holds an MD and a PhD — Theede occupies a practical position in the field: he is interested in what happens between a patient's last appointment and the next flare, and in whether the tools clinicians rely on are actually telling the truth. His research has appeared in journals ranging from *Clinical Gastroenterology and Hepatology* and *Journal of Crohn's & Colitis* to *EClinicalMedicine*, and he has been a consistent contributor to the Copenhagen IBD Cohort, one of the more carefully assembled real-world patient registries in Scandinavia. His entire published body of work is now indexed in the Bionoia corpus.
A Career Built Around the Monitoring Problem
The thread that runs most visibly through Theede's output is a preoccupation with a deceptively simple question: how do you know a patient with ulcerative colitis is truly in remission? Symptoms can mislead. Endoscopy is uncomfortable, resource-intensive, and carries small but real procedural risks. Theede's answer, pursued across multiple prospective studies, has largely been fecal calprotectin (FC).
In a cross-sectional study of 120 patients with active or inactive UC, he and colleagues demonstrated that FC levels correlate with both endoscopic inflammation scored by the Mayo Endoscopic Score and histological inflammation assessed on biopsy [id=175]. That finding has a practical corollary: FC can identify patients who have achieved mucosal healing without requiring a camera. A subsequent 12-month follow-up study tightened the argument further, showing that a baseline FC above 321 mg/kg predicted disease relapse and that histological inflammatory activity provided additional prognostic signal — even in patients whose Mayo endoscopic score was zero [id=174]. The implication is that histological healing, not just endoscopic healing, matters for long-term outcomes, and that FC can serve as a proxy worth taking seriously.
Earlier work had explored FC in a different but equally clinical context: monitoring UC during high-dose steroid treatment. In a prospective observational study of 16 patients, FC, CRP, and the Simple Clinical Colitis Activity Index all fell significantly over 27 days of treatment, with FC showing a mean decrease of 1,014 mg/kg (p = 0.006) [id=178]. That kind of granular, day-by-day data is rare and useful for clinicians making real-time decisions about steroid response.
Theede has also examined whether FC can be measured reliably outside a laboratory. A validation study comparing the IBDoc® point-of-care home testing kit against the BÜHLMANN fCAL® turbo laboratory assay found a strong correlation coefficient of 0.887 across 55 stool samples [id=171] — a result that supports the growing use of home monitoring in IBD, provided patients and clinicians understand its limits.
Smarter Use of Existing Drugs
A second strand of Theede's research concerns thiopurines — specifically, whether adding low-dose allopurinol to low-dose azathioprine improves outcomes while reducing toxicity. This combination shifts thiopurine metabolism away from hepatotoxic methylated metabolites and toward active 6-thioguanine nucleotides. Theede co-authored a pilot randomised trial of 46 IBD patients (UC and CD) showing that the combination was associated with a significantly higher rate of clinical remission at 24 weeks compared with standard azathioprine monotherapy [id=173]. That pilot fed into a larger, properly powered multicentre RCT — the AAUC trial — conducted at eight Danish hospital sites, which prospectively tested the combination in steroid-dependent or steroid-refractory UC patients over 52 weeks [id=166]. A nationwide Danish registry study of 10,367 IBD patients further contextualised the real-world use of this combination between 1999 and 2014 [id=169], providing population-level evidence to sit alongside the trial data.
A related question — what happens when anti-TNF therapy is withdrawn — was addressed in an observational study showing that optimising thiopurine therapy (targeting 6-thioguanine levels ≥150 nmol/mmol haemoglobin) before anti-TNF withdrawal was associated with low relapse rates in a cohort of 33 Crohn's disease patients followed for a median of 36 months [id=170].
Themes Across the Work
Looking across the full corpus, four through-lines emerge. First, *non-invasive monitoring*: FC as a proxy for mucosal and histological status is the most consistent methodological preoccupation. Second, *metabolite-guided thiopurine optimisation*: Theede has contributed to both trial and registry evidence that combination azathioprine-allopurinol therapy can be made safer and more effective with careful dose titration. Third, *endoscopic and histological endpoints as clinical anchors*: several studies use UCEIS, Mayo Endoscopic Score, and biopsy-based histological scoring not just as research instruments but as reference standards against which biomarkers are calibrated. Fourth, *safety of IBD therapy at the population level*: this includes a systematic review of post-operative complications in Crohn's patients on anti-TNF agents [id=177] and, more recently, a series of prospective Danish cohort studies examining COVID-19 susceptibility and outcomes in IBD patients — work that placed Theede within a large collaborative network tracking 319 UC and 197 CD patients through the pandemic period [id=167].
What This Means for the Field
Theede's body of work offers clinicians something genuinely practical: a connected set of studies that together make the case for FC-guided, endoscopy-calibrated, metabolite-informed IBD management — an approach that reduces unnecessary procedures without sacrificing prognostic precision. For Bionoia readers synthesising evidence on mucosal healing targets or monitoring strategies, his publications provide a coherent Danish dataset that complements larger international trials. The addition of his corpus to our platform means that evidence on biomarker thresholds, thiopurine combinations, and real-world IBD outcomes in a Nordic population is now fully searchable and cross-linked.