How rash and eschar came to clinical attention in scrub typhus and Japanese spotted fever

Early diagnosis of scrub typhus and Japanese spotted fever remains challenging because initial manifestations are often nonspecific. In endemic areas, nearly 30% of patients were not correctly diagnosed at the first visit to a participating site. Previous studies have mainly treated rash and eschar as present-or-absent findings. We examined how rash and eschar came to clinical attention in patients correctly diagnosed at the first visit to a participating site and in those diagnosed later.

We analyzed 217 patients with scrub typhus or Japanese spotted fever from three healthcare facilities in an endemic region of Japan. Because first-visit documentation was incomplete in many delayed-diagnosis cases, recognition-pattern variables were abstracted at the time the correct diagnosis was established. Among these patients, 156 (71.9%) were correctly diagnosed at the first visit to a participating site and 61 (28.1%) were diagnosed after one or more subsequent visits. In multivariable analysis, correct first-visit diagnosis was associated with rash reported as a chief complaint (adjusted odds ratio [aOR] 4.95, 95% confidence interval [CI] 2.07-11.84), rash elicited during history taking (aOR 5.86, 95% CI 2.80-12.27), eschar identified on physical examination (aOR 2.80, 95% CI 1.19-6.58), and eschar elicited during history taking, which was exclusively observed among patients diagnosed at the first visit to a participating site. Age 75 years or older was associated with lower odds of correct first-visit diagnosis (aOR 0.40, 95% CI 0.21-0.75).

In endemic settings, patients correctly diagnosed at the first visit to a participating site more often had rash and eschar brought to clinical attention in specific ways. Directed inquiry about skin symptoms and careful examination for eschar may help recognition in routine care.