Delayed Tetracycline Initiation Increases Mortality Risk in Patients With Japanese Spotted Fever: Retrospective Analysis Using a National Inpatient Database

Background: This study aimed to determine the relationship between time to tetracycline therapy initiation and disease outcome in patients hospitalized with Japanese spotted fever (JSF).

Methods: Patients with JSF enrolled in the Japanese Diagnosis Procedure Combination database from July 2010 to March 2021 were included in the analysis. Patients who received tetracycline on the day of admission were compared with those who received tetracycline later during their hospital stay using inverse probability of treatment weighting. The primary outcome was in-hospital mortality. Secondary outcomes were total hospitalization cost and length of hospital stay.

Results: A total of 1360 patients were included, of whom 1060 (78%) received tetracycline on the day of admission (early tetracycline group), and 300 (22%) received tetracycline later (delayed tetracycline group). Patients in the delayed tetracycline group had significantly higher in-hospital mortality than those in the early tetracycline group (3.9% vs 1.4%; odds ratio, 2.94; 95% CI, 1.34-6.47), significantly higher hospitalization costs, and longer hospital stays than those in the early tetracycline group.

Conclusions: The prognosis of patients with JSF is worse if tetracycline administration is delayed; therefore, physicians should initiate tetracycline on admission if JSF is suspected as a possible diagnosis.