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Primary Care

Response to antibiotics of women with symptoms of urinary tract infection but negative dipstick urine test results: double blind randomised controlled trial

BMJ 2005; 331 doi: (Published 14 July 2005) Cite this as: BMJ 2005;331:143
  1. Dee Richards, senior lecturer (derelie.richards{at},
  2. Les Toop, professor1,
  3. Stephen Chambers, professor2,
  4. Lynn Fletcher, biostatistician1
  1. 1 Department of Public Health and General Practice, Christchurch School of Medicine and Health Sciences, PO Box 4345, Christchurch, New Zealand
  2. 2 Department of Pathology, Christchurch School of Medicine and Health Sciences
  1. Correspondence to: D Richards
  • Accepted 15 May 2005


Objective To assess the effectiveness of antibiotic treatment of women with symptoms of urinary tract infection but negative urine dipstick testing.

Design Prospective, double blind, randomised, placebo controlled trial.

Setting Primary care, among a randomly selected group of general practitioners in Christchurch, New Zealand.

Participants 59 women aged 16-50 years presenting with a history of dysuria and frequency in whom a dipstick test of midstream urine was negative for both nitrites and leucocytes. Participants with complicated urinary tract infection were excluded.

Intervention Trimethoprim 300 mg daily for three days or placebo.

Main outcome measures Self reported diary of symptoms for seven days, recording the presence or absence of individual symptoms each day, followed by a structured telephone questionnaire after seven days. The main clinical outcome was resolution of dysuria at three and seven days and median time to resolution. Secondary outcomes were resolution of other symptoms.

Results The median time for resolution of dysuria was three days for trimethoprim compared with five days for placebo (P = 0.002). At day 3, five (24%) of patients in the treatment group had ongoing dysuria compared with 20 (74%) in the placebo group (P = 0.005). This difference persisted until day 7: two patients (10%) in the treatment group v 11 (41%) in the placebo group; P = 0.02). The number needed to treat was 4. The median duration of constitutional symptoms (feverishness, shivers) was reduced by four days.

Conclusions Although a negative dipstick test for leucocytes and nitrites accurately predicted absence of infection when standard microbiological definitions were used (negative predictive value 92%), it did not predict response to antibiotic treatment. Three days' treatment with trimethoprim significantly reduced dysuria in women whose urine dipstick test was negative. These results support the practice of empirical antibiotic use guided by symptoms. Balancing the competing interests of symptom relief and the minimisation of antibiotic use remains a dilemma—further research is needed to determine clinical predictors of response to antibiotics.


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  • This study would not have been possible were it not for the (unpaid) efforts of the general practitioners and practice nurses of the sentinel network who identified and recruited suitable patients. Research nurses Toni Stewart, Felicity Beats, and Margaret Sutherland were responsible for the data collection. Alison Parsons provided invaluable office support for the network and follow-up of missing data. Rosemary Ikram from Medlab South and Ben Harris from Southern Community Laboratories in Christchurch facilitated smooth identification and processing of results from all specimens.

  • Contributors DR and LT conceived and designed the study and interpreted the data. DR designed the protocol, coordinated the study, set up the database, participated in the data analysis and wrote the first draft of the paper with LT. SC advised on microbiological aspects of the design, planning, conduct, and analysis of the study and contributed to the writing of the paper. LF directed and carried out the statistical analysis, contributed to the writing of the paper, and took the lead in writing the sections on data analysis. DR is the guarantor.

  • Funding Health Research Council of New Zealand, an independent funding body.

  • Competing interests None declared

  • Ethics approval: Canterbury Ethics Committee.

  • Accepted 15 May 2005
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