Antibody protection to diphtheria in geriatric patients: Need for ED compliance with immunization guidelines

Study objective: Because 50% to 70% of geriatric patients have been shown to have nonprotective levels of tetanus antibodies, we postulated that this population might also have inadequate levels of diphtheria antibodies. Emergency physicians have the opportunity to immunize patients against tetanus and diphtheria. We sought to determine the seroprevalence of diphtheria anti-bodies in patients older than 65 years and to assess compliance with immunization guidelines in EDs. Methods: Enzyme-linked immunosorbent assay for diphtheria antibodies was conducted in 58 outpatients of a geriatric medical facility aged 65 years or older. We considered titers greater than .1 IU/mL protective. Eighteen ED personnel, ages 25 to 40 years, served as comparison subjects. The preparation used for immunization of injured patients-tetanus toxoid or tetanus and diphtheria toxoids adsorbed for adult use-was determined by means of a telephone survey of 64 New York City EDs. Results: The mean age of our patients was 80 years (range, 65 to 95 years). Their mean diphtheria antibody titer was 17 IU/mL (range, .04 to .54 IU/mL). Thirty-three percent (19 of 58; 95% confidence interval [CI], 21% to 45%) of patients had inadequate levels of diphtheria antibodies. We found no significant differences between protected and nonprotected patients with respect to age, sex, medical history, or military service. Patients with nonprotective levels of diphtheria antibodies were more likely to have inadequate tetanus antibody titers. Sixty-eight percent of patients without protection from diphtheria (13 of 19; 95% CI, 48% to 88%) were also unprotected from tetanus, and 33% (13 of 39; 95% CI, 19% to 47%) of those with adequate diphtheria antibodies had non-protective levels of tetanus antibodies (P=.012). All 18 ED personnel had adequate diphtheria and tetanus antibodies. The telephone survey revealed that 30% (19 of 64) of EDs use only tetanus toxoid for immunization of injured patients. Conclusion: A significant percentage of geriatric patients have inadequate diphtheria antibodies. Emergency physicians must comply with immunization guidelines for injured patients to assure adequate protection from both tetanus and diphtheria.