Consensus recommendations for ctDNA testing on pleural fluid and lavage

Design

Systematic review, national survey and two-round Delphi consensus

Population

27 studies; 109 survey respondents; 8-member expert panel

Primary outcome

Consensus recommendations for fluid-based ctDNA testing

Effect

15 recommendations, all agreed in round 1; 21.1% of respondents offered the test

Korean clinical practice guidelines in Annals of Laboratory Medicine (8 October) address circulating tumour DNA (ctDNA) testing on pleural effusion and bronchoalveolar lavage fluid in lung cancer. They were built from a targeted systematic review of 27 studies, a national survey of 109 laboratories and clinicians, and a two-round Delphi panel of eight experts.

Fifteen recommendations cover three areas: pre-analytical handling (four), analytical validation and quality management (four), and interpretation, reporting and clinical use (seven). All reached consensus in the first round. The evidence base was dominated by pleural effusion studies, with far fewer for lavage fluid. Only 21% of survey respondents offered fluid-based ctDNA testing, citing the lack of standard protocols, reimbursement and technical complexity.

Pleural fluid often arrives in the laboratory when tissue is scant, and its supernatant can carry more tumour DNA than plasma. For laboratories considering the test, the value of this document is a structured checklist for validation and reporting. The recommendations rest on expert consensus and mostly observational data, especially for lavage fluid.

• Validate any pleural fluid or lavage ctDNA assay separately from a plasma assay before reporting clinically.
• Standardise collection, processing time and supernatant handling for fluid specimens in a written protocol.
• State the specimen type and its limitations clearly on molecular reports from body fluids.
• Treat lavage-fluid ctDNA results with more caution than pleural fluid, given the thinner evidence.
• Consider fluid ctDNA where tissue is insufficient for molecular testing, after discussion with the treating team.

Why it matters

Pleural fluid is often the only sample available, and a validated fluid assay can spare a patient a second biopsy for molecular results.

Don't overread it

These are consensus recommendations from one country's panel, built on limited and mostly pleural-fluid evidence.

The statistics, in plain English

A Delphi process is a structured way of reaching expert agreement, not a measure of test accuracy. The 21% uptake figure reflects one national survey and may not apply elsewhere.

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