The risk of transfusion-transmitted syphilis in Australia is miniscule and there is a strong case for discontinuing universal blood donor screening for the disease, a new analysis concludes.

The current practice of donor serological testing for syphilis – which costs $4.4 million a year – could be replaced by targeted testing of male donors under 50 years of age while ensuring an acceptably low risk of transfusion-transmitted syphilis, a study by researchers from the University of Western Australia and the Australian Red Cross Blood Service has found.

Using data from syphilis screening results for blood donations made between 2009 and 2015, they calculate that the risk of transfusion-transmitted syphilis is one in 50 million transfusions with current practices, 1 in 4 million for targeted testing of first time donors and 1 in 2.8 million for no testing.

The researchers note that donor syphilis testing was introduced in the 1940s when the disease was common and before the use of antibiotics became widespread.

Since then the risk of syphilis transmission has been minimised by several factors including

• Low syphilis incidence in the community.
• Deferral practices for high risk donors.
• Blood storage at low temperatures that inactivate spirochaetes.
• Widespread antibiotic use in hospitals that inadvertently protects transfusion recipients.

The researchers note that serology testing of donors costs several million dollars a year and has drawbacks including false positives in autoimmune disease and viral infection.

In economic terms, current practices for syphilis screening have a cost of $539 million per disability‐adjusted life year (DALY) averted, whereas the accepted threshold for blood safety is $1 million/quality‐adjusted life year (QALY).

They therefore conclude that targeted screening of high risk donors, (males under the age of 50), would be an acceptable alternative, costing around $1.4 million a year, with a minimal increase in risk of transfusion-transmitted syphilis.

However, while there is a “compelling argument” to alter Australia’s blood donor syphilis testing strategy on cost effectiveness grounds, this has to be weighed against concerns about recent rises in syphilis rates in Indigenous communities and in gay men, they add.

“Recent changes in the epidemiology of syphilis in Australia and potential changes in the deferral periods for donors with higher risk sexual behaviours have resulted in key stakeholders concluding that it is not appropriate to consider reducing donor syphilis testing at this point in time,” they write in Vox Sanguinis.

“The Blood Service will continue to monitor changes in syphilis disease epidemiology and will revisit this decision once the impact of potential changes in donor deferrals are known and epidemiology changes are clearer, based on the strong argument presented in this study.”