Checking HbA1c Accuracy for Diabetes in Inflammatory Arthritis Patients Taking Sulfasalazine
Examines whether HbA1c reflects true blood sugar in arthritis patients taking sulfasalazine.
Plain-language title generated from the registry record
Registry title: Validation of Hemoglobin A1c in Patients With Inflammatory Arthritis Treated With Sulfasalazine
Key facts
- Where
- Silkeborg, DenmarkSee the site
AI summary: who the study is looking for
From the trial's eligibility criteria. Machine-read from the registry text on this page, so it can be wrong. The registry text below and the trial team decide who can take part.
The trial is looking for adults with inflammatory arthritis who take sulfasalazine and have either a diabetes diagnosis or a borderline HbA1c blood test.
- Age
- 18 years or older
- Sex
- All sexes can join
- Disease stage
- Inflammatory arthritis (rheumatoid arthritis, reactive arthritis, axial spondyloarthritis, psoriatic spondylitis or juvenile arthritis). Either a diabetes diagnosis of any type, or no diagnosis with HbA1c of 38 mmol/mol (5.6%) or higher.
- Earlier treatment
- Must have taken sulfasalazine for at least 2 months before joining. Must not have had glucocorticoids (injected or systemic) in the last 2 months.
- Biomarker or test result
- HbA1c of 38 mmol/mol (5.6%) or higher, measured at least 2 months after starting sulfasalazine, unless diabetes is already diagnosed.
Main reasons for not taking part
- Glucocorticoid treatment or injections in the last 2 months, or planned in the next 4 weeks
- Other conditions that disturb the HbA1c result, such as dapsone treatment
- Allergy to the adhesive used for the glucose sensor
- Cannot communicate in Danish
- Cannot decide for themselves, has cancer or is terminally ill
Read by machine on 9 November 2026.
Where in Denmark
- Medical Diagnostic CenterSilkeborg, DenmarkTaking people
Questions to ask the study team
- How often do I need to come in, and for how long each time?
- Are travel costs paid?
- Can I keep my own doctor?
- What happens if I want to stop?
Trial details
- Who runs it
- Klavs Würgler Hansen
- Trial code
- NCT07416656
- Record updated
- 25 June 2026
- Original description
The purpose of this study is to examine whether the blood test Hemoglobin A1c (HbA1c) gives an accurate picture of blood glucose levels in patients with inflammatory arthritis who are treated with sulfasalazine. HbA1c is widely used to diagnose and monitor diabetes, but sulfasalazine can shorten red blood cell lifespan and thereby lower HbA1c values independently of actual glucose levels.Read full original descriptionShow less
How Can We Prevent the Underdiagnosis of Diabetes and the Undertreatment of Known Diabetes in Patients With Inflammatory Arthritis Treated With Sulfasalazine?
The purpose of this study is to examine whether the blood test Hemoglobin A1c (HbA1c) gives an accurate picture of blood glucose levels in patients with inflammatory arthritis who are treated with sulfasalazine. HbA1c is widely used to diagnose and monitor diabetes, but sulfasalazine can shorten red blood cell lifespan and thereby lower HbA1c values independently of actual glucose levels.
This may lead to underdiagnosis of diabetes in patients who develop diabetes during sulfasalazine treatment, and to undertreatment in patients with known diabetes due to falsely reassuring HbA1c values.
The study aims to answer two main questions:
1. How many patients treated with sulfasalazine have undiagnosed diabetes despite having HbA1c values below the diagnostic threshold? 2. Does HbA1c underestimate actual glucose levels when compared with continuous glucose monitoring (CGM) in patients with sulfasalazine-treated inflammatory arthritis, both in those with known diabetes and those that are not diagnosed with diabetes but have borderline HbA1c values (≥ 38 mmol/mol)?
Inclusion: Age ≥18 years; Treatment with sulfasalazine for at least 2 months prior to inclusion; Inflammatory arthritis diagnosis (Reumatoid Arthritis, Reaktive Arthritis, Axial spa, Psoriatic spondylitis, and Juvenil artrit); HbA1c ≥38 mmol/mol obtained at least 2 months after sulfasalazine initiation OR a diabetes mellitus diagnosis (Type 1 diabetes mellitus, Type 2 diabetes mellitus, Malnutrition-related diabetes mellitus, Other specified diabetes mellitus (andre specificerede former for diabetes), and Unspecified diabetes mellitus (uspecificeret diabetes)); Can communicate in Danish; Informed consent including permission to upload glucose data and study ID to the Libreview Platform.
Exclusion: Systemic treatment or local injections with glucocorticoids within the previous 2 months or planned within the following 4 weeks; Allergy towards the adhesive used in the CGM; Considered ineligible for participating (e.g. patients without decision-making capacity, , malignancy, terminal illness, ect.); Clinical conditions interfering with the interpretation of HbA1c expect for sulfasalazine alterations in red cell lifespan (etc. Dapson treatment).