Editorial Annals of Clinical Biochemistry 2014, Vol. 51(4) 421–423 ! The Author(s) 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/0004563214531236 acb.sagepub.com
Pleural fluid biochemistry – old controversies, new directions Rahul Bhatnagar1,2 and Nick Maskell1,2
Pleural effusions are a common reason for presentation to medical services. Many effusions have similar fluid appearances, and clinical history and examination may provide definitive treatment plans in only a small percentage of cases. Biochemical analysis of pleural fluid has long been a front-line tool for the respiratory physician, with relatively simple, common tests often able reliably to guide patient management. The British Thoracic Society (BTS) guideline for the management of pleural disease was first published in 2003.1 This document generated substantial debate amongst clinical biochemists.2 Specific concerns included a lack of detail in the advice provided to clinicians regarding how to prepare samples for analysis, and the absence of specialist laboratory advice in the creation of the guidelines. There were also arguments against the use of pH as a routine test, including the fact that as a pleural investigation it is not specific for any particular disease (pH may be low, for example, in malignancy, pleural infection or rheumatoid arthritis), and that samples need to be collected anaerobically, requiring the use of blood gas analysers outside of their licence. In 2010, the BTS released an updated pleural disease guideline.2 This document was prepared over a threeyear period and involved consultation with a wide range of organizations, including the Royal College of Pathologists and The Association for Clinical Biochemistry. Although it addressed many of the points of contention from the 2003 document, some disputed recommendations remain. Over the last few years there has been a concerted drive to move the management of pleural disease into the outpatient setting, enabled by the rapid expansion of dedicated pleural and ‘admission-avoidance’ clinics.3 To be successful, these rely on the relevant diagnostic information being immediately available to clinicians
using the minimum number of procedures. In our experience, this approach results in almost 95% of new pleural effusion patients avoiding admission for intercostal tube drainage, and the heavy costs this entails. Throughout the 2010 guideline there is an acceptance that biochemical tests must be interpreted in the light of clinical information and this is particularly important in the case of pH measurement due to its relative lack of specificity. However, while we agree that pleural fluid pH need not be measured in all samples taken, especially in those which are clearly purulent (this has the potential to damage machines), appropriate point-of-care analysis of pH remains one of the few tests that can significantly alter a patient’s immediate management course. The BTS guidelines recommend that patients with suspected pleural infection and an effusion pH of
Pleural fluid biochemistry – old controversies, new directions Rahul Bhatnagar1,2 and Nick Maskell1,2
Pleural effusions are a common reason for presentation to medical services. Many effusions have similar fluid appearances, and clinical history and examination may provide definitive treatment plans in only a small percentage of cases. Biochemical analysis of pleural fluid has long been a front-line tool for the respiratory physician, with relatively simple, common tests often able reliably to guide patient management. The British Thoracic Society (BTS) guideline for the management of pleural disease was first published in 2003.1 This document generated substantial debate amongst clinical biochemists.2 Specific concerns included a lack of detail in the advice provided to clinicians regarding how to prepare samples for analysis, and the absence of specialist laboratory advice in the creation of the guidelines. There were also arguments against the use of pH as a routine test, including the fact that as a pleural investigation it is not specific for any particular disease (pH may be low, for example, in malignancy, pleural infection or rheumatoid arthritis), and that samples need to be collected anaerobically, requiring the use of blood gas analysers outside of their licence. In 2010, the BTS released an updated pleural disease guideline.2 This document was prepared over a threeyear period and involved consultation with a wide range of organizations, including the Royal College of Pathologists and The Association for Clinical Biochemistry. Although it addressed many of the points of contention from the 2003 document, some disputed recommendations remain. Over the last few years there has been a concerted drive to move the management of pleural disease into the outpatient setting, enabled by the rapid expansion of dedicated pleural and ‘admission-avoidance’ clinics.3 To be successful, these rely on the relevant diagnostic information being immediately available to clinicians
using the minimum number of procedures. In our experience, this approach results in almost 95% of new pleural effusion patients avoiding admission for intercostal tube drainage, and the heavy costs this entails. Throughout the 2010 guideline there is an acceptance that biochemical tests must be interpreted in the light of clinical information and this is particularly important in the case of pH measurement due to its relative lack of specificity. However, while we agree that pleural fluid pH need not be measured in all samples taken, especially in those which are clearly purulent (this has the potential to damage machines), appropriate point-of-care analysis of pH remains one of the few tests that can significantly alter a patient’s immediate management course. The BTS guidelines recommend that patients with suspected pleural infection and an effusion pH of
