Trace element levels in pleural effusions

TABLE 1 Patients and pleural fluid characteristics Patient characteristics (n = 105) Male, n (%) 66 (62.9%) Age, mean (SD) 66 (12.6) Diagnosis, n (%) Fluid overload 21 (20.0%) Benign exudate 26 (24.8%) MPE 58 (55.2%) Pleural effusion characteristics Median IQR Biochemistry Glucose (mmol/L) 5.6 [4.4-6.8] LDH (IU/L) 267 [161-697] pH 7.36 [7.27-7.42] Protein (g/L) 38 [28-45] Trace elements a Zinc (μmol/L) 6.1 [3.3-8.7] Copper (μmol/L) 9.2 [5.85-16.2] Cobalt (nmol/L) 1.6 [1.1-2.6] Manganese (nmol/L) 10.7 [5.6-17.5] Iron (μmol/L) 7.5 [3.5-16.8] Molybdenum (nmol/L) 7.9 [5.1-16.9] a Limit of detection is 3 × SD of the blanks and the limit of quantification is 10 × SD of blanks. Trace element levels according to pleural effusion groups: fluid overload (n = 21), benign exudates (n = 26) and malignant pleural effusions (MPE) (n = 58). *P [less than] .05; **P [less than] .01; ***P [less than] .001 DISCUSSION This study is the largest on trace elements in pleural fluid in a well-phenotyped cohort. Interestingly, iron, as well as overexpression of manganese superoxide dismutase and copper-zinc superoxide dismutase, has been implicated in carcinogenesis of asbestos-related cancers. 10,11,14 Copper-complexed disulfiram has a proposed role against mesothelioma. 15 The role of trace elements in pleural malignancies may deserve further exploration. Not surprisingly, trace element levels lack value in separating effusions into benign and malignant. 4-6,16-18 Given the diverse effects of trace elements, it is likely that they are involved in basic mechanisms underscoring different disease processes and are present in significant concentrations across disease states.