Incidence, risk factors and distribution of syphilis in the end-stage renal disease population in the USA

Background: Syphilis is a sexually transmitted infection with an incidence of 14.9 cases per 100 000 persons in the USA in 2011. Untreated syphilis may remain quiescent for years but can also result in clinical sequelae, including neurosyphilis. End-stage renal disease (ESRD) patients may be at risk for syphilis due to a higher incidence of risk factors for the disease, including human immunodeficiency virus (HIV). Despite the presence of these risk factors, the incidence of syphilis in the ESRD population has not been reported. To address this issue, we investigated the incidence and risk factors for syphilis in the ESRD population using the United States Renal Data System (USRDS).

Methods: This study analyzed incident ESRD patients from 2004 to 2010. Based on International Classification of Diseases, Ninth Revision codes for syphilis, we determined the incidence and risk factors for syphilis following an inpatient diagnosis. Generalized linear modeling was used to examine the relative risk (RR) for the disease when controlling for demographic and other clinical risk factors.

Results: A total of 383 diagnoses of syphilis were identified after screening 759 066 patients. The 8-year incidence of any type of syphilis was 50.45 cases per 100 000 person-years. Other unspecified syphilis (29.77 cases per 100 000 person-years) and neurosyphilis (10.93 cases per 100 000 person-years) were the most common diagnoses. The greatest incidence was found on the East and West Coasts. Patients with the disease were younger and more likely to be black and non-Hispanic. In the final model, the adjusted RR for syphilis was significantly increased with HIV (7.61), hepatitis C (3.57), herpes simplex (2.06) and hepatitis B (1.75).

Conclusions: The incidence of syphilis is >3-fold greater in ESRD patients when compared with the general population and is associated with sexually transmitted viral infections. Neurosyphilis is a common occurrence and is treatable, suggesting that all assessments of confusion in dialysis patients should include screening for the disease.