Pleural effusion found (tests before aspiration)
BioMG follows French guidelines. Adapt it to the guidelines and the tests available where you practise.
Unexplained unilateral effusion
Laboratory tests (blood, to enclose with the letter for the tap)
- FBC
- Total serum protein
- Serum LDH (Light's criteria)
- Serum electrolytes
- Urea
- Serum creatinine
- Liver function tests: ALT
- Alkaline phosphatase
- Bilirubin
- NT-proBNP (if heart failure possible)if needednon-French guidelineSuspected heart failure: serum NT-proBNP is sensitive and specific for attributing a unilateral effusion to heart failure (conditional recommendation), without being interpreted in isolation [2].
- INR (if on a vitamin K antagonist)if needednon-French guidelinePatient on a vitamin K antagonist (VKA): if the VKA is interrupted before a scheduled puncture, it is stopped 5 days before and the INR is checked before the procedure (target ≤ 1.5) [3].
- Serum albumin (if heart failure or cirrhosis possible)if needednon-French guidelineIn Spain, the SEPAR recommendation advises calculating the serum-pleural fluid albumin difference when heart failure is suspected with a borderline exudate: if this difference exceeds 12 g/L, the effusion is considered a transudate, which applies to 83% of these false exudates of cardiac origin; in hepatic hydrothorax classified as an exudate, the pleural fluid/serum albumin ratio is below 0.6 in 77% of cases [4]. The French teaching reference also proposes this gradient when in doubt, almost 20% of transudates being wrongly classified as exudates, for example on diuretics [5]. The British recommendation on which this page is based does not mention it [2].
Do not order
- Tumour markers and other serum biomarkers (CEA, CA 15-3, CRP, etc.) to diagnose a malignant, infectious or autoimmune pleural effusion: not to be used at present [2]
- Serum tuberculosis biomarkers as a routine (outside high-prevalence areas): not recommended [2]
- PT and aPTT as a routine before puncture: useless without a history of coagulopathy or anticoagulant treatment [3]
Bilateral effusion
Laboratory tests (general causes)
- NT-proBNP
- Serum albumin
- Serum creatinine with eGFR
- ASTif needednon-French guidelineLiver failure is among the causes of bilateral effusion [2].
- ALTif needednon-French guidelineLiver failure is among the causes of bilateral effusion [2].
- Bilirubinif needednon-French guidelineLiver failure is among the causes of bilateral effusion [2].
- PTif needednon-French guidelineLiver failure is among the causes of bilateral effusion [2].
- Urine protein:creatinine ratio (if oedema, hypoalbuminaemia)if needednon-French guidelineNephrotic syndrome and hypoalbuminaemia are among the causes of transudate [2]. See the “Proteinuria” page.
Also consider
- Signs of heart failure? If heart failure is probable, follow the page "Heart failure".
Sources (7)
- Psallidas I, Rahman NM. Advances in pleural disease (éditorial). Eur Respir Rev 2016;25(140):108-109.
- Roberts ME, Rahman NM, Maskell NA, et al. British Thoracic Society Guideline for pleural disease. Thorax. 2023;78(Suppl 3):s1-s42.
- Asciak R, Bedawi EO, Bhatnagar R, et al. British Thoracic Society Clinical Statement on pleural procedures. Thorax. 2023;78(Suppl 3):s43-s68.
- Villena Garrido V, Cases Viedma E, Fernández Villar A, et al. Recommendations of diagnosis and treatment of pleural effusion. Update. Arch Bronconeumol. 2014;50(6):235-49.
- Collège des enseignants de pneumologie (CEP, SPLF). Item 206 – Épanchement pleural liquidien. Référentiel pour la préparation des épreuves dématérialisées nationales, 9e édition, 2026.
- Shen-Wagner J, Gamble C, MacGilvray P. Pleural effusion: diagnostic approach in adults. Am Fam Physician. 2023;108(5):464-475.
- Jany B, Welte T. Pleural effusion in adults: etiology, diagnosis, and treatment. Dtsch Arztebl Int. 2019;116(21):377-386.