Chest
Volume 117, Issue 1, January 2000, Pages 87-95
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Clinical Investigations
PLEURAL DISEASE
Pleural Fluid pH as a Predictor of Pleurodesis Failure: Analysis of Primary Data

https://doi.org/10.1378/chest.117.1.87Get rights and content

Study objectives

To determine the predictive accuracyof pH for identifying patients with malignant pleural effusions whowill fail pleurodesis.

Design

Analysis of publishedand unpublished individual patient-level data retrieved from a MEDLINEsearch and correspondence with primary investigators.

Studyselection

Studies that reported pleural fluid pH values andoutcomes of pleurodesis for patients with malignant pleuraleffusions.

Data collection and analysis

Primaryinvestigators supplied data for 433 patients. Receiver operatingcharacteristic analysis and logistic regression estimated thepredictive accuracy, decision thresholds, and value of pleural fluid pH compared with other clinical factors. The primary investigations weregraded for study design.

Results

Pleural fluid pH wasthe only independent predictor of pleurodesis failure (odds ratio,4.46; 95% confidence interval [CI], 2.69 to 7.45; p < 0.0001) andhad an area under the receiver operating characteristic curve (decisionthreshold, ≤ 7.28) of 0.671 (95% CI, 0.624 to 0.715). The pH modelfit the data well (p = 0.48) with the probability of pleurodesisfailure increasing as pH decreased; specificity and negative predictivevalues for pleurodesis failure exceeded 90% and 80%, respectively, with a positive predictive value of 45.7% at pH values ≤ 7.15. Theprimary studies had several important design limitations.

Conclusions

Using patient-level data, this study showedthat pleural fluid pH has only modest predictive value for predictingsymptomatic failure and should be used with caution, if at all, inselecting patients for pleurodesis. The limitations of the primary studies and low predictive accuracy should be considered when usingpleural fluid pH for patient care.

Section snippets

Article Selection

We searched MEDLINE for pertinent articles using pH, pleural fluid, pleural effusions, pleural malignancy, malignant effusions, and pleurodesis as key words. The articles were examined to determine whether reference was made to the utility of pH for predicting pleurodesis outcome for patients with documented malignant pleural effusions. The reference lists of relevant articles were reviewed to identify additional articles and abstracts. We also queried several experts on pleural disease and the

Sources of Information

The data search identified 11 articles,4, 56, 78, 910, 1112, 13, 14 4 abstracts,25, 2627, 28 and 1 letter 29 that reported outcomes of pleurodesis and pH values. All of the abstracts were excluded because their data were subsequently reported in the retrieved articles. The letter reported data that partially overlapped with a subsequent article; the investigator supplied data for these patients, which allowed the removal of duplicate data from analysis.

One investigator indicated that

Discussion

Our analysis of original, patient-level data from published studies demonstrates that pleural fluid pH has only modest (AUC, 0.671) discriminative properties for identifying patients who will experience symptomatic failure of pleurodesis. Pleural fluid pH did not have a greater predictive accuracy when compared by ROC analysis to glucose or %LDH for predicting symptomatic failure. Although pleural fluid pH had only modest discriminative properties, it was the only pleural fluid test that was an

ACKNOWLEDGMENTS

The authors thank Drs. Steven A. Sahn and Marc Silverstein for reviewing the manuscript.

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