ORIGINAL ARTICLE Predictive models for diagnosis of pleural effusions secondary to tuberculosis or cancer ROBERTA K.B. SALES, FRANCISCO S. VARGAS, VERA LUIZA CAPELOZZI, MÁRCIA SEISCENTO, EDUARDO H. GENOFRE, LISETE R. TEIXEIRA AND LEILA ANTONANGELO Pulmonary and Clinical Laboratory (ICHC) Divisions, Heart Institute (InCor), University of São Paulo Medical School, São Paulo, Brazil ABSTRACT Background and objective: Tuberculosis (TB) and cancer are two of the main causes of pleural effusions which frequently share similar clinical features and pleural fluid profiles. This study aimed to identify diag- nostic models based on clinical and laboratory vari- ables to differentiate tuberculous from malignant pleural effusions. Methods: A retrospective study of 403 patients (200 with TB; 203 with cancer) was undertaken. Univariate analysis was used to select the clinical variables rel- evant to the models composition. Variables b coeffi- cients were used to define a numerical score which presented a practical use. The performances of the most efficient models were tested in a sample of pleural exudates (64 new cases). Results: Two models are proposed for the diagnosis of effusions associated with each disease. For TB: (i) adenosine deaminase (ADA), globulins and the absence of malignant cells in the pleural fluid; and (ii) ADA, globulins and fluid appearance. For cancer: (i) patient age, fluid appearance, macrophage percentage and presence of atypical cells in the pleural fluid; and (ii) as for (i) excluding atypical cells. Application of the models to the 64 pleural effusions showed accuracy higher than 85% for all models. Conclusions: The proposed models were effective in suggesting pleural tuberculosis or cancer. Key words: adenosine deaminase, cancer, globulin, pleural cytology, pleural effusion, tuberculosis. INTRODUCTION Tuberculosis (TB) and cancer are two of the main causes of pleural effusions. The accumulated fluid results from injury to the pleura with consequent changes in the homeostasis of the pleural space. 1 According to the World Health Organization, Brazil has the 16th highest incidence of TB worldwide. Pleural disease is the most common extrapulmonary form of TB in adults, comprising 14.4% of all cases. 2,3 The gold standard for the diagnosis of pleural TB is the recovery of bacilli from pleural fluid or tissue. The low positivity of bacilloscopy (<10%) and culture (15– 30%) is notorious and is related to the small number of bacilli in the fluid. Culture also requires up to 6 weeks for the organism to grow. The presence of granuloma (85%) and a positive culture (55%) in pleural biopsy specimens shows high diagnostic sen- sitivity, but the procedure is more complex and inva- sive and requires specialized laboratory and medical training. 4,5 The incidence of pleural effusion secondary to cancer is also high, with an estimated incidence of 150 000 cases per year in the USA. 1 Malignant pleural disease is defined by the finding of tumour cells in pleural fluid (42–96%) or tissue (40–75%). 6 The lower positivity obtained with closed pleural biopsies is mainly related to disease stage and extent of infil- tration as well as the randomness of the biopsy sampling. 7,8 Given these difficulties, a combination of labora- tory methods that might increase diagnostic sensitiv- ity should be considered. The objective of the present study was to establish low cost and low complexity models using clinical and laboratory variables that could provide an accurate diagnosis of malignancy or TB. Correspondence: Roberta K.B. Sales, Rua Itapeva 500, Cjto 4C, Bela Vista, S. Paulo 01332-000, Brazil. Email: roberta.sales@ uol.com.br Received 14 January 2009; invited to revise 17 February 2009, 21 April 2009; revised 8 April 2009, 30 April 2009; accepted 30 April 2009 (Associate Editor: Jose Porcel). Editor in Chief sign off date: David Hui, 3 July 2009. SUMMARY AT A GLANCE Diagnostic models to distinguish between tuber- culous and malignant pleural effusions in a country with a high prevalence of tuberculosis (TB) were developed and validated. We recom- mend the application of these models for a quick and presumptive diagnosis as they are based on routine clinical and laboratorial variables. © 2009 The Authors Journal compilation © 2009 Asian Pacific Society of Respirology Respirology (2009) 14, 1128–1133 doi: 10.1111/j.1440-1843.2009.01621.x