Adaptive D-dimer strategies had a 0.5% failure rate in patients ruled out above 500

Design

Systematic review and meta-analysis of prospective diagnostic management studies

Population

12,194 patients with suspected PE managed by adaptive D-dimer strategies, 6 studies

Primary outcome

3-month diagnostic failure after PE ruled out without imaging

Effect

Overall 0.12% (0.06–0.26%); adaptive window 0.50% (0.20–1.11%); I² 0%

Age-adjusted and clinical-probability-adjusted D-dimer thresholds, such as those in the YEARS and PEGeD approaches, allow imaging to be withheld in patients whose D-dimer is above the traditional 500 ng/mL. Most validation of these rules has been post hoc, in patients actually managed with the fixed cut-off, which leaves doubt about the patients they newly exclude.

This systematic review and meta-analysis pooled six prospective management studies, with 12,194 patients and PE prevalence of 7% to 19%, in which an adaptive threshold actually guided imaging. Diagnostic failure was venous thromboembolism or PE-related or unexplained death within three months. Among everyone in whom PE was ruled out without CT pulmonary angiography, the failure rate was 0.12% (95% CI 0.06–0.26%). In the 'adaptive window' — D-dimer above 500 but below the adapted threshold — it was 0.50% (0.20–1.11%). Heterogeneity was zero for both. The strategies avoided imaging in about 61% of patients.

A failure rate of around 0.5% in the adaptive window sits within what is usually accepted for diagnostic strategies for PE, though it is higher than for those below 500. The data come from prospective use, which is the evidence earlier critiques asked for. Pregnant women and children were excluded.

• Use an age-adjusted or probability-adjusted D-dimer threshold in non-pregnant adults with non-high clinical probability.
• Expect about 0.5% three-month failures in patients ruled out with a D-dimer just above 500.
• Adaptive strategies avoided CT pulmonary angiography in about six in ten patients across the studies.
• These data do not cover pregnancy or children; use pathways designed for those groups.
• Give safety-net advice to return with worsening symptoms after PE is ruled out without imaging.

Why it matters

It answers the safety question about exactly the patients adaptive thresholds spare from scanning.

Don't overread it

The failure rate is higher in the adaptive window than below 500; adaptive thresholds trade a small rise in misses for many fewer scans.

The statistics, in plain English

A failure rate of 0.50% with an upper limit of 1.11% means at most about 1 in 90 patients in the adaptive window may have PE missed, and probably about 1 in 200. I² of 0% means the studies agreed closely.

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