There are a few guidelines recommend about management of eosinophilia worldwide, most of guielines recommend a thorough history-taking and physical examination. Subsequently, investigations are requested based on suspected causes. In cases where parasite infection is suspected, particularly in developing countries, stool microscopy and serology are recommended. However, limitations such as low sensitivity of stool microscopy, the inconvenience of collecting multiple stool samples, and the high cost and unavailability of serology may arise. Consequently, some physicians opt for empiric anthelminthic regimens in managing eosinophilic patients, even without stool tests or if stool test results are normal. If subsequent complete blood count (CBC) results show a recovery of absolute eosinophil count, it is assumed that eosinophilia was caused by a parasite infection. While some studies demonstrate the efficacy and simplicity of this approach, there is a risk of overestimating parasite infection in eosinophilic patients, potential adverse drug reactions from unnecessary anthelminthic treatment, and the possibility of drug resistance due to inappropriate dosing. To address this gap, no study has yet compared the efficacy between specific anthelminthic treatment based on test results and empirical anthelminthic treatment in eosinophilic patients. Therefore, the investigators are conducting this study.

Eosinophilia is defined as an absolute eosinophil count exceeding 500 cells per microliter, calculated by multiplying the white blood cell count by the percentage of eosinophils.

Cause of eosinophilia vary from mild to life-threatening disease. Prevalence of each cause of eosinophilia vary on study population, the most common etiology in developing country is parasite infection.

Stool microscopy can be conducted using various methods. The Kato-Katz technique, recommended by the WHO, exhibits a sensitivity of only 52.4 percent (95%CI = 47.6 - 57.1 percent). More sensitive methods for parasite detection in stool, such as stool culture or PCR, are not readily available and can be costly. In the intervention group of this study, the investigators employed three different parasite detection methods (stool microscopy, stool culture, and PCR) to enhance sensitivity in detecting parasites.

Inclusion Criteria:

• Participants who come for check-ups at general practitioner, primary care unit, and Srivejchavat Premium Center have an absolute eosinophil count greater than 500 cells/microliter with a white blood cell count less than 10,000 cells/microliter.
• Age at least 18 years old
• Consent to participate in research

Exclusion Criteria:

• Having any characteristics that need urgent care 1.1 Having history of unintended significant weight loss is defined as the loss of body weight exceeding 10% within a span of six months without deliberate attention.

1.2 Physical examination revealed a body temperature equal to or greater than 37.8 degrees Celsius, lymphadenopathy or hepatosplenomegaly.

1.3 CBC revealed blast cell

• Receiving anthelminthic drug within 6 months
• Underlying cancer (active stage), HIV, HBV, HCV, collagen vascular disease, active TB
• Allergy to albendazole, ivermectin, or metronidazole
• Pregnancy or lactation
• Serum transaminase higher than 2 times of upper normal limit
• Taking medications that may induce eosinophilia within the past three months, such as herbal supplements, NSAIDs, Salicylic acid, Carbamazepine, Colchicine, Nitrofurantoin, Dapsone, or Minocycline, was reported.

The datasets used and/or analyzed during the current study are available at primary researcher and may share with author research on reasonable request.