Interventions
The intervention group was given a prescription for antibiotics with instructions to fill it after 3 days if symptoms failed to improve. The control group received a prescription with instructions to start taking the antibiotic medication immediately. General practitioners prescribed any antibiotic that they considered most appropriate. In both groups, patients were advised to return to see their doctor if symptoms worsened.
Data collection
At recruitment, the patient’s temperature was taken and the list of symptoms was recorded in duplicate. The patient was asked to take his or her temperature daily with a digital thermometer (Assess Diagnostics Medical Industries Australia Pty. Ltd., 148-152 Regent St., Redfern NSW 2016, Australia) that was provided. Patients were given symptom checklists to complete daily for 10 days after the visit. Symptoms listed were dry cough, night cough, sneezing, sore throat, pain on inspiration, pain when coughing, hoarse voice, headache, staying home from work or unable to do normal daily tasks, unwell, diarrhea, vomiting, and nausea without vomiting. Patients were instructed to record whether they had a runny nose with clear secretions (“clear runny nose”), stuffy (blocked) nose, or runny nose with dark secretions (“colored runny nose”). Patients further checked off whether they had clear sputum only in the morning, colored sputum in the morning, clear sputum all day, or colored sputum all day.
A point was allocated for each symptom. The maximum possible score was 15.16 A study assistant telephoned all participants on day 3, day 7, and day 10 to ask about their temperature and symptoms. At the end of the study, the research assistant asked participants about their level of satisfaction with the consultation, using the questions and scoring system devised by Little et al.11 Although no data were collected about revisit rates, data were collected about the patient’s intention to visit a physician for the next cold.
Outcomes and analysis
The outcomes were antibiotic use, symptom scores, and the responses to satisfaction-related questions asked at the end of the study. Outcomes of intervention and control groups were compared on an intention-to-treat basis.17 Because of the repeated measures, the temperatures and summary scores of symptoms were determined with the general linear mixed model that uses Statistical Analysis System (SAS, Cary, N.C.), version 8, for Windows. Chi-square determinations and the Mantel-Haenszel odds ratio were performed for discrete variables using Statistical Package for the Social Sciences (SPSS), version 10, for Windows. When the final data point for continuous variables was missing, the last recorded value was analyzed as the current value. For discrete values, worst-case and best-case scenarios were performed. The sample size of 212 patients was based on a reduction from 60% of antibiotics consumed immediately to 40% in the delayed-prescription group (alpha 0.05, beta 0.2).
Allocation and masking
The unit of randomization was the patient. N.K., who was not a recruiter, generated the allocation schedule with Excel 97. Letters containing instructions for the intervention strategy pertaining to each patient or allocating the patient to the control group were placed in opaque envelopes and sealed. The study number was written on the outside of the envelope according to the randomization schedule. The envelopes were then given to the research assistant, who placed them in a large brown envelope with the consent forms and information sheets for recruiting family physicians. The recruiters opened each envelope immediately after recruitment of each patient.
Patients were told only that they would be given 1 of 2 sets of instruction about taking antibiotics for their colds. Participants read an information sheet and then completed a consent form. Thus, patients were blind to what the other group would take. The research assistant asked the participants not to tell her which instructions they had been given for taking antibiotics. If both types of blinding had been followed correctly, this study could be described as double blinded. However, because we cannot confirm the effectiveness of blinding the research assistant, we prefer to call this study single blinded. One copy of the allocation schedule was kept in the office of N.K.; another was kept by the departmental secretary.
Results
The Figure shows the trial profile summarizing participant flow. The baseline characteristics of the patients in both groups were similar (Table 1).
Patients in the delayed prescription group were less likely to use antibiotics (48%, 95% CI, 35%-60%) than those in the “take antibiotics now” group (89%, 95% CI, 76%-94%). The odds ratio for not using antibiotics was 0.12 (95% CI, 0.05 to 0.29) using intention-to-treat analysis. By antibiotic use, we mean that the patients consumed at least 1 dose of the antibiotic medication.