A practical workup for eosinophilia - You can investigate the most likely causes right in your office

The vast majority of cases of eosinophilia in North America are caused by a llergic processes. In individual cases, a short differential diagnosis of t he most likely causes can be formulated on the basis of the absolute eosino phil count. The extensive laboratory workup previously recommended by some authorities is probably not justified unless detailed history taking and ph ysical examination indicated a need for specific investigations. Although t he possibility of missing an occult neoplasm has been used to justify exten sive investigation, this is usually not necessary because most tumor-associ ated eosinophilia is accompanied by widely metastatic disease. History taki ng should emphasize the possibility of drug-induced or helminth-associated eosinophilia. If the history indicates travel, dietary or other exposure ri sks, stool examination for ova and parasites is worthwhile. If a possible a llergic cause is suspected, testing for evidence of atopy may be performed concomitantly with testing for parasitic infection. A follow-up white blood cell count with differential is recommended to ascertain whether eosinophi lia has resolved. When an absolute eosinophil count of more than 1.5 x 10-d egrees/L persists for longer than 6 months, idopathic hypereosinophilic syn drome must be ruled out.