Retrospective study of pleural parasitic infestations: a practical diagnostic approach

Pleural parasitic infestation (PPI) is a disease prevalent in certain parts of the world. It is frequently misdiagnosed due to its lack of standardized diagnostic criteria. The purpose of this study was to evaluate the clinical characteristics of PPI patients and develop a practical diagnostic approach for PPI.

A retrospective study was conducted by reviewing the medical records of 11 patients with PPI. A practical diagnostic approach was proposed based on the unique laboratory findings.

All patients demonstrated respiratory symptoms, including shortness of breath, cough, fever, chest pain, excessive sputum and hemoptysis. Leukocytosis (> 10,000/μL) and eosinophilia (> 500/μL) of peripheral blood were present in 45.5 and 36.4% patients, respectively. The mean concentrations of pleural effusion lactate dehydrogenase (LDH), adenosine deaminase (ADA), protein and carcinoembryonic antigen (CEA) were 338.2 U/L (range, 61–667 U/L), 11.6 U/L (range, 0.1–28.2 U/L), 43.7 g/dL (range, 21.9–88.1 g/dL), and 1.84 mg/mL (range, 0.28–4.8 mg/mL), respectively. The mean percentage of eosinophils in the pleural effusion was 19.5% (10.5–41%). Blood test was positive for parasite-specific IgG antibody in 9 patients, including 4 for Paragonimus westermani, 3 for Taenia solium, 1 for Clonorchis sinensis and 1 for Echinococcus granulosus. Eggs of Clonorchis sinensis were detected in the stool of two patients. Sparganum was found in the pleural effusion of one patient. Respiratory symptoms and abnormal appearances in pulmonary radiographic examination were disappeared in all patients who received anti-parasitic treatment.

In patients with unexplained pleural effusion, parasite-specific IgG antibody tests should be performed when pleural fluid testing shows eosinophilic pleural effusion. It is preferable to consider the diagnosis of PPI in clinical practice when serum parasite-specific IgG antibody test is positive.