Background People who present to the emergency department often do not know their tetanus immunisation status. The Protetanus test can determine whether a person is immune and can guide treatment decisions.

Objectives To examine whether testing all patients for immunity is clinically advisable and cost-effective.

Methods 200 patients presenting to the emergency department with wounds were asked whether they were covered for tetanus, not covered or did not know. All had their tetanus immunity tested with the Protetanus kit and the result was compared with reported status. The number of unnecessary vaccinations which might have been given based on recall was calculated. The cost of testing and subsequent treatment versus vaccinations based on recall was calculated.

Results 136 (68%) tested positive for tetanus immunity; 64 (32%) were negative. Age, sex and nationality were not associated with tetanus immunity. 151 (75.5%) did not know their status. Of these, 101 (66.9%) were positive and 50 (33.1%) negative. 49 (24.5%) were sure of their status. 36 said they were covered of whom 10 (27.8%) were wrong. 13 said they were not covered of whom 9 (69.2%) were wrong. If vaccination were based on recall status 38.8% of patients would receive incorrect treatment. Testing all 200 and treating appropriately would save £984, or £4.92 per patient compared with vaccination based on recall.

Conclusion On clinical grounds testing is advisable and it may produce significant cost savings.