Azithromycin cleared the bacteria and changed nothing

Design

multicentre, randomised, placebo-controlled trial; stopped for futility at planned interim analysis; separate analysis of bacteria-positive and bacteria-negative cohorts

Population

840 children aged 18-59 months presenting to an emergency department with moderate-to-severe wheezing; 521 positive for pathogenic bacteria

Primary outcome

sum of Asthma Flare-up Diary for Young Children scores over 5 days (range 5-35)

Effect

positive cohort median 9.59 vs 9.72 (P=0.70); negative cohort 9.30 vs 9.10 (P=0.69); bacterial clearance 58.7% vs 11.4%

AZ-SWED randomised 840 children aged 18 to 59 months presenting to an emergency department with a moderate-to-severe wheezing episode to azithromycin 12 mg/kg daily for five days or matching placebo. The rationale was reasonable: children with recurrent wheeze more often carry Streptococcus pneumoniae, Moraxella catarrhalis and Haemophilus influenzae in the nasopharynx, and 521 of the 840 tested positive. Efficacy was assessed separately in the positive and negative cohorts.

The data and safety monitoring board stopped the trial for futility at a planned interim analysis. Symptom scores over five days were indistinguishable in the positive cohort (median 9.59 against 9.72, P = 0.70) and the negative cohort (9.30 against 9.10, P = 0.69). Length of stay, hospital stay and 72-hour return visits were similar. Resistance and adverse events did not differ.

The instructive part is the dissociation. Azithromycin cleared the bacteria — 58.7% against 11.4% in the positive cohort — and the children were exactly as unwell. A positive nasopharyngeal culture in a wheezing preschooler is therefore not an indication to treat; the organism is present but is not driving the illness. That is a stronger argument against antibiotics in this presentation than any stewardship policy, because it answers the clinical intuition rather than overriding it.

• Do not prescribe azithromycin for acute preschool wheeze, whatever the nasopharyngeal flora
• Do not send nasopharyngeal cultures in this presentation — a positive result does not change management
• Treat the wheeze: bronchodilator, oxygen and steroid where indicated
• Reserve antibiotics for a separate documented bacterial infection, not for the wheezing episode
• Azithromycin remains a common over-the-counter purchase in India for childhood wheeze — this gives a specific answer for that conversation

Why it matters

It separates carrying a pathogen from being made ill by one, in the presentation where that confusion drives most paediatric antibiotic prescribing.

Don't overread it

This concerns acute wheezing episodes in 18- to 59-month-olds, not azithromycin as prophylaxis in recurrent wheeze or in chronic lung disease.

The statistics, in plain English

Stopping for futility means the interim data showed the trial could not plausibly reach a positive result even if it ran to completion — a stronger statement than a non-significant final P value. Median scores differing by 0.13 on a 5-to-35 scale is a difference far below anything a parent or clinician could perceive.

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