SCOUT: what the UTI trial adds to UK primary care prescribing

Lower urinary tract infection in women is one of the most common reasons for antibiotic prescribing in UK primary care. NICE NG109 currently positions nitrofurantoin as first-line where renal function permits, with pivmecillinam and fosfomycin as alternatives. The SCOUT trial, published in the Lancet on 20 April 2026, is the first pragmatic head-to-head comparison of all four commonly used regimens in a single trial. The results reinforce rather than redraw the UK prescribing picture, but they do sharpen one question in particular.

The trial

SCOUT randomised 768 women aged 18 or older across Spanish primary care between April 2022 and November 2024. All had at least one UTI-specific symptom (dysuria, urgency, frequency, or suprapubic tenderness) and a positive urine dipstick for nitrite or leukocyte esterase. They were allocated in a 1:1:1:1 ratio to one of four treatments: a single 3g dose of fosfomycin, two 3g doses of fosfomycin on consecutive days, nitrofurantoin 100mg three times daily for 5 days, or pivmecillinam 400mg three times daily for 3 days. The primary outcome was clinical resolution, defined as disappearance of all UTI symptoms, at day 7. The trial was open-label.

The authors concluded that nitrofurantoin was the most effective regimen and single-dose fosfomycin the least effective, with adverse events reported as mild across all arms. Their overall position, reflected in an accompanying Lancet commentary, was that single-dose fosfomycin's role as a first-line option warrants reconsideration.

Three caveats for UK prescribers

For UK prescribers, three caveats frame how to read this.

First, SCOUT is an open-label pragmatic trial with a patient-reported primary endpoint. Open-label designs can favour regimens that patients or clinicians expect to be more effective. Differences observed are therefore associative rather than definitive.

Second, the trial was conducted in Spain, where uropathogen resistance patterns differ from the UK. Direct extrapolation of effect sizes to English practice should be made cautiously, and local resistance data remain the primary reference for empirical choice.

Third, the trial did not stratify outcomes by suspected or confirmed resistant organisms, so the results apply to unselected empirical prescribing rather than to the specific scenario in which fosfomycin is often chosen in UK practice — suspected or confirmed ESBL-producing organisms.

What SCOUT adds

What SCOUT adds, read against those limits, is randomised evidence across four commonly used options within a single protocol. It does not on its own redraw NICE NG109 positioning of nitrofurantoin as first-line. It does prompt a useful question for practices and local antimicrobial stewardship groups: where fosfomycin is chosen — whether as a convenience option for women who decline a multi-day course or for other reasons — is the two-dose regimen a clinically preferable default to the single-dose regimen? SCOUT suggests the two-dose arm performed better than single-dose in this trial, though neither matched nitrofurantoin.

References

1. Llor C, et al. Clinical and bacteriological effectiveness of three different short-course antibiotic regimens and single-dose fosfomycin for uncomplicated lower urinary tract infections in women (SCOUT): a pragmatic, multicentre, open-label, randomised clinical trial. Lancet. 20 April 2026. thelancet.com

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