Diagnostic yield of small-bowel capsule endoscopy in patients with iron-deficiency anemia: a systematic review

Background: Iron-deficiency anemia (IDA) is the most common cause of anemia worldwide. Current guidelines recommend the use of small-bowel capsule endoscopy (SBCE) in IDA. Evidence of the validity of SBCE in patients with IDA alone is still limited.

Objective: To assess the diagnostic yield (DY) of SBCE in IDA by pooling data from relevant studies.

Design: Systematic review and meta-analysis. Fixed-effects or random-effects models were used as appropriate.

Setting: Studies that estimated the DY of SCBE in IDA were identified. Two investigators independently conducted the search and data extraction.

Patients: A total of 24 studies enrolling 1960 patients with IDA who underwent SBCE were included.

Main outcome measurements: Per-patient DY, with 95% confidence intervals. Subgroup analysis was also performed.

Results: The pooled DY of SBCE in IDA, evaluated by a random-effects model, was 47% (95% CI, 42%-52%), but there was statistically significant heterogeneity among the included studies (inconsistency index [I(2)] = 78.8%, P < .0001). The pooled DY of SBCE in studies focused solely on patients with IDA (subset 1, 4 studies) was 66.6% (95% CI, 61.0%-72.3%; I(2) = 44.3%); conversely, that of studies not focusing only on IDA patients (subset 2, 20 studies) was 44% (95% CI, 39%-48%; I(2) = 64.9%). In particular, more vascular (31% vs 22.6%, P = .007), inflammatory (17.8% vs 11.3%, P = .009), and mass/tumor (7.95% vs 2.25%, P < .0001) lesions were detected with SBCE in patients participating in the studies in subset 1.

Limitations: Heterogeneity of studies, retrospective design, and selection bias.

Conclusions: This analysis demonstrates the validity of SBCE in the investigation of patients with IDA and negative findings on a previous diagnostic workup, although certain factors such as heterogeneity and quality of the included studies should be taken into account.