Evaluation of the Clinical Specificity of the Active Anthrax Detect™ Plus (AAD Plus) Lateral Flow Immunoassay (LFI)

This study is a multi-site trial assessing the clinical specificity of AAD Plus using capillary blood, venous blood, and venous serum samples collected from presumptive anthrax negative subjects who present with symptoms consistent with cold, flu or other bronchial and febrile infections in the US. At least 440 subjects who meet the study eligibility criteria will have 3 blood samples from a single time point tested with the AAD Plus device. The samples will be: 1) capillary blood collected by finger stick; 2) venous blood collected in a sodium citrate anticoagulant tube; and, 3) serum obtained from venous blood collected in a serum separator tube. The capillary blood sample will be tested immediately to avoid clotting by an unblinded staff member. The venous blood and serum samples will be tested by a blinded staff member as soon as possible after preparation. Additional aliquots of the serum sample will be prepared and stored frozen at -20 ± 2°C or colder for possible additional reference testing [CDC reverse-transcriptase polymerase chain reaction (RT-PCR) assay (K140426)] in the event that any of the subject's capillary blood, venous blood, or serum sample is positive.

At each clinical site, subjects' paired venous whole blood and serum samples will be randomly selected such that 10% of all subjects' samples (total of 40) will be spiked with recombinant anthrax lethal factor (LF) to prepare a contrived positive sample. Each clinical site will be provided a unique randomization list by the Data Management Center that identifies, which subjects will be randomized for spiking with LF. The numbers of spiked samples will be distributed approximately equally between all sites. An unblinded site staff member will prepare the blinded, spiked (from 40 subjects selected for spiking) and unspiked (from 400 subjects that are not selected for spiking) venous blood and serum specimens to be tested by a blinded staff member. Before the venous blood sample and serum specimens (from subjects selected for spiking) are spiked; the unblinded staff member will also test all unspiked samples on the AAD Plus and record the results. Then the spiked venous blood and serum sample will be given to the blinded staff member for testing. Thus, blinded staff will receive whole blood and serum samples that could be either unspiked (presumed negative) or spiked (presumed positive) to preserve the blind. In the rare event that the AAD Plus test result is positive on the unspiked sample tested by the unblinded staff member, then the unblinded staff member will give the unspiked sample from this subject to the blinded operator for AAD Plus testing and the subject's serum sample will be sent for reference testing as described above. Blinded staff will remain blinded throughout the study to the contrived spiking of the whole blood and serum samples as to which samples were contrived.