Given the poor ability of stool examination to diagnose strongyloides, detecting antibodies by ELISA can be useful. Serology can cross-react with other parasites, remain positive for years after successful treatment or be falsely negative in immunocompromised patients. Infected patients will also often have an elevated eosinophil count, with an average of absolute eosinophil count of 1000 in one series. Eosinophilia of a gastrointestinal infection may fluctuate in response to larval output, or may be permanently lacking in some disseminated infections. Hence lack of eosinophilia is not evidence of absence of infection. The combination of clinical suspicion, a positive antibody and a peripheral eosinophilia can be strongly suggestive of infection.