VHOSPITAL.CLINIC · Diagnostic Test
Blood eosinophilia (>0.5 × 10⁹/L) is the first laboratory sign of ascariasis during larval migration — providing the critical clue that triggers parasitological investigation when pulmonary or systemic symptoms are present.
Peripheral eosinophilia peaks during the larval migration phase (Loeffler syndrome, weeks 1–3) when larvae pass through the liver and lungs. By the adult intestinal phase, eosinophilia may normalise. Eosinophilia alone is not diagnostic but is the key 'alarm signal' that directs further testing.
Standard venous blood sample for complete blood count (CBC/FBC) with differential. The absolute eosinophil count (AEC) is the key value: mild eosinophilia (0.5–1.5 × 10⁹/L), moderate (1.5–5 × 10⁹/L), severe (>5 × 10⁹/L). In ascariasis, eosinophilia is typically moderate during Loeffler syndrome.
Eosinophilia >0.5 × 10⁹/L in a patient with respiratory symptoms → consider Loeffler syndrome (ascariasis or other larvae). Eosinophilia in intestinal phase → lower or normal. Eosinophilia with transient pulmonary infiltrates on chest X-ray = Loeffler syndrome — stool O&P at 8–10 weeks confirms Ascaris eggs.
Eosinophilia sensitivity for Ascaris (larval phase): 60–80%. Specificity: low — many causes of eosinophilia exist. Eosinophilia in the adult intestinal phase: only 30–50% of patients. Not a stand-alone diagnostic test — must be interpreted with clinical context and stool examination.
Eosinophilia is a response to tissue-invasive parasites — the immune system releases eosinophils to attack larvae breaching tissue barriers. Adult Ascaris worms residing in the intestinal lumen (without tissue invasion) provoke a much weaker eosinophilic response, so eosinophilia is often normal in established intestinal infection.
Major differential diagnoses include: other helminths (hookworm, Toxocara, Strongyloides, schistosomiasis), drug reactions (NSAIDs, antibiotics), atopic conditions (asthma, eczema), eosinophilic oesophagitis, Addison's disease, and malignancy (Hodgkin lymphoma). Travel history and stool examination help differentiate.
Yes. Eosinophil counts typically normalise within 4–6 weeks after successful antihelminthic treatment. Persistent or rising eosinophilia after treatment suggests re-infection, treatment failure, or an alternative diagnosis requiring further investigation.
Full Blood Count (Eosinophilia) helps confirm Ascariasis, which can cause these symptoms:
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