Study Objective: To determine whether the measurement of pleural fluid pH in malignant effusions has diagnostic use, predicts survival, and has therapeutic implications.
Design: A prospective comparison of cytologic examinations and pleural biopsy results, survival, and response to chemical pleurodesis with tetracycline in patients with normal-pH (7.30 or greater) and low-pH (less than 7.30) malignant pleural effusions.
Setting: Academic medical center, university referral hospital, city hospital, and Veterans Administration hospital.
Patients: Sixty patients with malignant pleural effusions, proven at either initial thoracentesis by cytologic examination or within 4 months of initial thoracentesis by repeat thoracentesis, thoracotomy, or autopsy, were followed until death.
Intervention: Twenty-one patients, 12 with normal pleural fluid pH and 9 with low pleural fluid pH, were treated with tube thoracostomy and intrapleural tetracycline for symptomatic, recurrent pleural effusions.
Main Results: The 20 patients with low-pH malignant effusions had a significantly greater positivity on initial pleural fluid cytologic evaluation, a shorter mean survival, and a poorer response to tetracycline pleurodesis compared with 40 patients with normal-pH malignant effusions.
Conclusions: Determination of pleural fluid pH in malignant effusions provides a rational approach to further diagnostic testing, prognostic information, and a rationale for palliative treatment.