Ferritin across long-term conditions in England: cross-sectional primary care study
Discuss this preprint
Start a discussion What are Sciety discussions?Listed in
This article is not in any list yet, why not save it to one of your lists.Abstract
Background
Iron deficiency (ID) is a readily treatable condition once identified. Ferritin is the primary diagnostic marker, but cut-offs vary and inflammation complicates interpretation in patients with long-term conditions (LTCs).
Aim
To describe ferritin distribution and the prevalence of threshold-defined low ferritin in adults with and without LTCs in primary care.
Design and setting
Cross-sectional observational study using routinely collected electronic health records from a national primary care database in England (1 st January 2015 to 31 st December 2021).
Method
Adults with ≥1 ferritin test in Clinical Practice Research Datalink (CPRD) Aurum were included. LTCs were identified using validated primary-care code lists. Outcomes included ferritin distribution and threshold-defined ID prevalence using World Health Organization (WHO) (<15 µg/L; <70 µg/L if inflammation) and National Institute for Health and Care Excellence (NICE) (<30 µg/L) cut-offs, stratified by sex and, in women, by age <50 versus ≥50 as a proxy for menopausal status.
Results
4,489,594 individuals were included; 55% (n=2,469,882) had ≥1 LTC. Ferritin was lowest in women <50 and in LTCs characterised by impaired absorption or blood loss (coeliac disease, inflammatory bowel disease). Among women <50 with an LTC, 80% had ferritin <70 µg/L versus 47% <30 µg/L, leaving 33% in the 30–70 µg/L range potentially missed by standard cut-offs; equivalent figures were 28% in women ≥50 and 17% in men.
Conclusion
Threshold-defined low ferritin is very common across LTCs and disproportionately affects women, particularly those under 50. Condition-specific, inflammation-adjusted ferritin thresholds may improve detection, management, and equity in primary care.
