ADA/CRP ratio may help differentiate Tuberculous from Malignant pleural effusion
Tuberculous pleural effusion (TPE) and malignant pleural effusion (MPE) display similar cytological and biochemical pictures, including adenosine deaminase (ADA). One of the novel and cost-effective tools for differentiating MPE from TPE could be the pleural fluid ADA to serum CRP ratio (ADA/CRP). The major challenge is scarce data available to support the effectiveness. The available evidence needs to be more comprehensive and consistent. However, in a recent study published in BMC Pulmonary Medicine, Dr Mohammad Fazle Rabbi and colleagues have concluded that the Pleural fluid adenosine deaminase to serum C-reactive protein ratio (ADA/CRP) ratio improves the diagnostic usefulness of ADA for TPE.
This cross-sectional study in the National Institute of Diseases of the Chest and Hospital (NIDCH), Mohakhali, Dhaka, evaluated the diagnostic accuracy of pleural fluid ADA to serum CRP ratio to discriminate between tuberculous and malignant pleural effusion. (July 2021 to February 2022). The included patients were diagnosed with TPE and MPE. A receiver operating characteristic curve (ROC) was constructed for identifying TPE. The added value of the ADA/CRP ratio to ADA was evaluated using the net reclassification improvement (NRI) and integrated discrimination improvement (IDI).
Histopathological investigations are required to differentiate between TPE and MPE. Differentiation is challenging, and histopathology is invasive. Considering this, researchers investigated whether the ratio ADA/CRP adds diagnostic value to ADA.
Key results of the study are:
A total of 59 patients were enrolled, out of which 31 had TPE and 28 had MPE.
· In patients with TPE, Pleural fluid ADA to serum CRP ratio and pleural fluid ADA level were higher.
· There was no significant difference in serum CRP levels between TPE and MPE patients.
· At a cut-off value of > 1.25, pleural fluid ADA to serum CRP ratio had a sensitivity and specificity of 93.8% and 85.2%, respectively.
· The positive and negative predictive values were 88.2% and 92%, respectively, in the diagnosis of TPE.
· The area under the ROC curve was 0.94.
In this study, the NRI and IDI analyses revealed the added diagnostic value of ADA/CRP to ADA.
This is the first study adding additional diagnostic value of ADA/CRP over ADA, but some of the limitations acknowledged by the researchers are small size sample, inclusion of only tuberculous and malignant pleural effusion cases, tissue culture was not performed, therefore delaying treatment and complicating the cases.
They said larger sample sizes are required to validate the findings, and the inclusion of other causes of exudative effusion is required to get more comprehensive details.
Reference:
Rabbi, M.F., Ahmed, M.N., Patowary, M.S.A. et al. Pleural fluid adenosine deaminase to serum C-reactive protein ratio for diagnosing tuberculous pleural effusion. BMC Pulm Med 23, 349 (2023). https://doi.org/10.1186/s12890-023-02644-9
