The frequent exacerbator phenotype in bronchiectasis has been defined by a threshold of three or more exacerbations a year. This analysis of the European Bronchiectasis Registry asks whether that threshold means anything.
It covered 19,324 patients across 30 countries in Europe and Asia, using negative binomial regression over up to five years of follow-up, with severe exacerbations defined as those requiring hospitalisation.
Risk rose smoothly with each prior event. Compared with none, the incidence rate ratio for future exacerbations was 1.45 (95% CI 1.34 to 1.58) after one prior exacerbation, 1.84 (1.69 to 1.99) after two, 2.50 (2.29 to 2.73) after three, and 3.56 (3.32 to 3.82) after four or more. There is no step at three — the curve simply keeps climbing.
Severity carried its own weight. A single prior severe exacerbation raised future exacerbation risk by 52% and future severe exacerbation risk almost four-fold (incidence rate ratio 3.96, 95% CI 3.71 to 4.22). The pattern held across aetiologies and geographic regions.
The practical consequence is that a patient with two exacerbations in the past year is not 'below threshold' — they are at nearly twice the risk of someone with none, and the current definition would exclude them from consideration for preventive treatment. Treating the count as a continuous risk marker rather than a gate is the change.
The single severe exacerbation finding is the most actionable. One hospitalisation identifies a patient at four-fold risk of another, and that patient deserves a full aetiological workup, airway clearance review and sputum culture before they are discharged and lost.
- Stop treating three exacerbations a year as a threshold — risk rises continuously from the first event
- A patient with two exacerbations last year is at 84% higher risk of further events than one with none
- Treat a single hospitalised exacerbation as a strong marker: four-fold risk of another severe event
- Use a hospitalisation as the trigger for aetiological workup, sputum culture and airway clearance review
- The pattern held across aetiologies and regions, so it applies regardless of underlying cause
The statistics, in plain English
Incidence rate ratios here compare rates of repeated events rather than the odds of a single one, which is the right model when patients can exacerbate many times. The intervals are all narrow — 3.32 to 3.82 for the four-or-more group, for example — because the registry contains 19,324 patients, so these are precisely estimated. Precision is not the same as causation: this is observational registry data, and prior exacerbations mark underlying disease severity rather than causing future events. That distinction matters for prognosis, which is what the paper supports, and not for any claim that preventing one exacerbation reduces the risk of the next.
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