Diagnostic Yield After Negative Bidirectional Endoscopy for Iron Deficiency Anaemia: A Single-Centre Audit of Downstream Investigations in the UK Two-Week-Wait Pathway.

BACKGROUND: Iron deficiency anaemia (IDA) accounts for a significant proportion of all gastroenterology referrals. Current British Society of Gastroenterology (BSG) guidance recommends bidirectional endoscopy as first-line investigation and reserves small-bowel or renal-tract investigation for patients with recurrent IDA or inadequate response to iron replacement therapy (IRT) after negative endoscopy. Advanced imaging modalities represent high financial costs to the NHS, but their diagnostic yield in this specific cohort is debated.

OBJECTIVE: To describe the utilisation and observed diagnostic yield of downstream investigations following negative bidirectional gastrointestinal endoscopy in patients referred via the IDA two-week-wait (2WW) pathway, and to discuss the implications for resource use within this clinical pathway. This audit was exploratory and was not designed as a formal health-economic evaluation.

METHODS: We performed a retrospective single-centre audit of all consecutive adult patients investigated on an IDA 2WW pathway during the study period. Demographic data, biochemical confirmation of IDA, completion of baseline investigations, endoscopic findings, cancer detection, and downstream investigations after negative endoscopy were reviewed. Denominators are reported for each analysis; no imputation was performed.

RESULTS: A retrospective audit was conducted on all patients referred via the IDA 2WW pathway to a single UK secondary care centre between January 2024 and March 2025. Eighty-nine patients were included; the mean age was 71.3 (10.1) years, and 46/89 (51.7%) were male. IDA was biochemically confirmed in 89/89 (100%). Oesophagogastroduodenoscopy (OGD) and colonoscopy were performed in 76/89 (85.4%) and 69/89 (77.5%), respectively; complete bidirectional endoscopy was achieved in 66/89 (74.2%). Cancer was identified in 9/89 patients (10.1% (95% CI 4.7 to 18.3)). Overall, endoscopy was negative in 54/89 (60.7% (95% CI 49.7 to 70.9)); among those completing bidirectional endoscopy, 43/66 had negative examinations (65.2% (95% CI 52.4 to 76.5)). In the negative-endoscopy cohort, capsule endoscopy was performed in 1/54 (1.9% (95% CI 0.0 to 9.9)) and CT/MR enterography in 7/54 (13.0% (95% CI 5.4 to 24.9)). Repeat IDA was documented in 28/54 (51.9% (95% CI 37.8 to 65.7)), but an alternative cause was identified on further testing in only 1/54 patients (1.9% (95% CI 0.0 to 9.9)).

CONCLUSIONS: In this audit, downstream investigations after negative endoscopy were used infrequently and identified few additional clinically actionable diagnoses. These findings support selective, guideline-concordant follow-up after high-quality negative bidirectional endoscopy, particularly in patients with recurrent or refractory anaemia, but should be interpreted cautiously given the single-centre design, limited follow-up, and low use of advanced imaging.