A transfusion medicine physician in California reports that she is struggling to develop a reasonable algorithm for determining which post-donation illness reports should qualify for a 120 day 'possible' West Nile Virus (WNV) deferral. According to her interpretation of the FDA guidance document (Section III C), it is recommended "that donors who report an otherwise unexplained post-donation febrile illness with headache or other symptoms suggestive of WNV infection (i.e., flu-like symptoms that include fever with headache, eye pain, body aches, generalized weakness, new skin rash or swollen lymph nodes or other evidence of WNV infection) within two weeks after donation within the typical WNV season ... be deferred for 120 days following the onset of illness. She asks "Now that we are within the WNV season, what is the appropriate algorithm for determining which post-donation illnesses qualify for the 120 day deferral?" She assumes that it would not be desirable to assign a 120 day deferral to every donor with a febrile illness or even every donor with fever with headache or fever with body aches. To get a better understanding of West Nile Fever, she reports having reviewed an article entitled Clinical Characteristics and Functional Outcomes of West Nile Fever. Ann Intern Med 2004;141:360-5 (full text pdf) which surveyed 98 patients diagnosed with West Nile Fever. In these patients, the most outstanding symptoms (%, median duration) were fatigue (94%, 36 days), fever (79%, 5 days), headache (70%, 10 days), and muscle aches (61%, 14 days). Vomiting and diarrhea were present in approximately 25% of patients and upper respiratory symptoms in less than 20% of patients. The main problem with this study is that it is subject to ascertainment bias, as only individuals suspected of having WNV fever would have been tested for WNV and diagnosed with West Nile Fever. In some states (including our own), the state does not offer testing unless the fever lasts for at least 7 days. The California physician would be interested in learning how blood centers are defining post donation illnesses that require a 120 day deferral. The answers to the following questions would be of particular interest:

1. Would you defer individuals with post donation febrile illness for 120 days only if you have WNV cases identified in your local geographic area? If so, what prevalence of infection in your area would be your trigger to assign the 120 day deferral to donors with post donation febrile illness?
2. Are you eliciting a travel history from every donor with post donation fever, in order to determine whether they have been to a WNV endemic region?
3. Is there a particular symptom complex or duration period for symptoms that would lead you to assign the 120 day deferral or to exclude the donor from requiring a 120 day deferral?

Please submit comments to the e-Network Forum.

Ira A. Shulman, MD
CBBS e-Network Forum Editor & Moderator