Validation of Calprotectin As a Novel Biomarker For The Diagnosis of Pleural Effusion: a Multicentre Trial

Abstract

Discriminating between malignant pleural effusion (MPE) and benign pleural effusion (BPE) remains difficult. Thus, novel and efficient biomarkers are required for the diagnosis of pleural effusion (PE). The aim of this study was to validate calprotectin as a diagnostic biomarker of PE in clinical settings. A total of 425 patients were recruited, and the pleural fluid samples collected had BPE in 223 cases (53.7%) or MPE in 137 patients (33%). The samples were all analysed following the same previously validated clinical laboratory protocols and methodology. Calprotectin levels ranged from 772.48 to 3,163.8 ng/mL (median: 1,939 ng/mL) in MPE, and 3,216-24,000 ng/mL in BPE (median: 9,209 ng/mL; p < 0.01), with an area under the curve of 0.848 [95% CI: 0.810-0.886]. For a cutoff value of ≤ 6,233.2 ng/mL, we found 96% sensitivity and 60% specificity, with a negative and positive predictive value, and negative and positive likelihood ratios of 96%, 57%, 0.06, and 2.4, respectively. Multivariate analysis showed that low calprotectin levels was a better discriminator of PE than any other variable [OR 28.76 (p < 0.0001)]. Our results confirm that calprotectin is a new and useful diagnostic biomarker in patients with PE of uncertain aetiology which has potential applications in clinical practice because it may be a good complement to cytological methods. The diagnosis of pleural effusion (PE) is a clinical challenge because it can be produced by over 60 diseases 1,2. Nevertheless, in clinical practice the priority is to establish whether the PE is malignant or not. A diagnosis of malignant PE (MPE) implies the presence of advanced-stage tumours and is therefore associated with a poor prognosis 1,3 which requires urgent diagnosis. Thoracocentesis is the first and most simple procedure for the diagnosis of PE 2-4. Unfortunately, while its specificity for establishing malignancy is 100%, the diagnostic sensitivity of pleural fluid (PF) cytological analysis is low. Although the odds of establishing an MPE diagnosis by immunohistochemistry are improved by applying a panel of different antibodies, its diagnostic sensitivity is still only approximately 60% for metastatic PE and less than 30% for mesothelioma 5,6. When the cytology results are negative, more invasive methods such as a pleural biopsy or thoracoscopy are necessary 2,4,7. In this context, more groups are searching for PF biomarkers for malignancy with the aim of avoiding these invasive procedures 8-10. Recent meta-analyses have evaluated the ability of new biomarkers such

Calprotectin in Lung Diseases

“…In a cohort of 425 patients, pleural CLP levels ranged from 772.48 to 3163.8 ng/mL (median: 1939 ng/mL) in malignant PEs, and 3216–24,000 ng/mL in non-malignant PEs (median: 9209 ng/mL) [ 90 ]. For a cut-off value of ≤6233.2 ng/mL, a 96% sensitivity and 60% specificity were reported in discriminating malignant from non-malignant PEs [ 90 ], suggesting pleural CLP as a novel and useful diagnostic biomarker in patients with PE of uncertain etiology [ 90 , 92 ].…”

Pleural biomarkers in diagnostics of malignant pleural effusion: a narrative review

“…It was finally found that calprotectin showed a considerably high diagnostic accuracy for MPE (AUC, 0.96). However, these results were not confirmed by three subsequent studies (41)(42)(43), which showed that the diagnostic accuracy (i.e., the AUC) of calprotectin in MPE was 0.68 (41), <0.50 (42), and 0.85 (43), respectively. This results inconsistency may be attributable to the wide disease spectrum in the different study cohorts, as well as to the use of different calprotectin assays.…”

A rapid calprotectin test for the diagnosis of pleural effusion

“…However, these studies were limited, among other factors, by the small number of patients in which calprotectin was determined in our research laboratories. Thus, we carried out this multicentre study to validate calprotectin levels in PE as a diagnostic biomarker of malignancy in clinical settings [ 7 ]. In this study, calprotectin levels were measured using the conventional robotised equipment and employing the enzyme-linked immunosorbent assay (ELISA fCA ® , Bühlmann Laboratories) routinely used in our laboratory [ 7 , 8 ].…”

“…Thus, we carried out this multicentre study to validate calprotectin levels in PE as a diagnostic biomarker of malignancy in clinical settings [ 7 ]. In this study, calprotectin levels were measured using the conventional robotised equipment and employing the enzyme-linked immunosorbent assay (ELISA fCA ® , Bühlmann Laboratories) routinely used in our laboratory [ 7 , 8 ]. The results of this work were useful when making early clinical decisions about the treatment of these patients because the use of this marker can lead to better diagnoses and can help avoid possible adverse consequences.…”

“…This assay is based on lateral flow technology and is not time consuming. Given that ELISA fCAL ® is the only calprotectin measurement method that has been evaluated for use with PF to date [ 8 ], to confirm the clinical validity of QB ® sCAL we correlated its results with those from the ELISA fCAL ® method used in our previous multicentre study [ 7 ].…”