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Evidence-Based Dermatology: Research Commentary
March 2003

Antibiotic Prophylaxis for Lyme Disease: How the Way of Reporting a Clinical Trial Can Alter the Perception of Effectiveness

Author Affiliations

MichaelBigbyMDRosamariaCoronaDSc, MDDamianoAbeniMD, MPHPaoloPasquiniMD, MPHMoysesSzkloMD, MPH, DrPHHywelWilliamsMSc, PhD, FRCP

Arch Dermatol. 2003;139(3):373-375. doi:10.1001/archderm.139.3.373

Question: Is a single 200-mg dose of doxycycline effective for preventing Lyme disease after an Ixodes scapularis tick bite?

Design: Nadelman et al conducted a randomized, double-blind (patients and study personnel), placebo-controlled clinical trial over a period of 9.5 years (May 1987 to December 1996) to determine the effect of a single dose of doxycycline on prevention of Lyme disease after a tick bite. Some patients were included twice during this time. At baseline and at 3 weeks' and 6 weeks' follow-up, patients were interviewed and examined, and serum antibody tests were performed and blood cultures done for Borrelia burgdorferi. A randomization list was used to maintain a 1:1 ratio. Patients swallowed the pills under direct observation of study personnel. Sample size calculations were clearly defined. The trial included 506 patients with 482 meeting the inclusion parameters (235 doxycycline, 247 placebo) and who had removed identifiable I scapularis ticks from their bodies. Twenty-eight had removed multiple ticks at the time of the enrollment bite. Species, sex, and stage of ticks were determined by a medical entomologist. Ticks were initially classified as unfed (flat) or partly fed (partially engorged) on the basis of a visual inspection. When possible, the tick's attachment time to the subject was estimated on the basis of a measurement of the tick body. Specific questions regarding the adverse effects of doxycycline use were added to a questionnaire. Additional subjects were enrolled after it was discovered that the risk of erythema migrans was limited to subjects who had been bitten by nymphal ticks (to obtain a sample size with enough statistical power).

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