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Martin Lund,1 Torben B Pedersen,1 Søren Feddersen,2,3 Louise D Østergaard,1,3 Charlotte A Poulsen,1 Christian Enggaard,2 Mads HA Poulsen,1,3 Lars Lund1,3 1Department of Urology, Odense University Hospital, Odense, Denmark; 2Department of Clinical Biochemistry and Pharmacology, Odense University Hospital, Odense, Denmark; 3Department of Clinical Research, University of Southern Denmark, Odense, DenmarkCorrespondence: Lars Lund, Department of Urology, Odense University Hospital, Sdr. Boulevard 29, Odense, 5000, Denmark, Tel +45 5140 8982, Fax +45 6541 1726, Email Lars.Lund@rsyd.dkPurpose: Serum levels of the polypeptide chemokine C-C motif ligand 2 (CCL2) have previously shown potential as a prostate cancer diagnostic and prognostic biomarker. Plasma CCL2 levels may be superior to serum levels as a biomarker because of their potentially lower signal-to-noise ratio.Materials and Methods: Before initiating a large comparative study of plasma and serum CCL2 levels, we performed a prospective, diagnostic pilot study Of 133 individuals from a clinically relevant population. CCL2 plasma levels were measured using a validated assay kit. Plasma was obtained independently of digital rectal examination.Results: In this pilot study, we found no relationship between CCL2 plasma values and risk of proven prostate cancer, whereas previous studies found a strong diagnostic relationship between CCL2 serum values and prostate cancer.Conclusion: Our contribution to the existing literature strengthens the idea that early in the pathological process, CCL2 mainly circulates in large, membrane-enclosed compartments, whereas plasma CCL2 levels increase markedly during disease progression. We conclude that whereas plasma CCL2 levels are not useful as a diagnostic measure, a ratio of CCL2 plasma to serum levels may prove useful as a marker of disease progression, which warrants further study.Keywords: diagnostics, liquid biopsy, CCL2, monocyte chemoattractant protein 1, MCP1

Diagnostic studies of accuracy targeting sensitivity and specificity are commonly done in a paired design in which all modalities are applied in each patient, whereas cost-effectiveness and cost-utility analyses are usually assessed either directly alongside to or indirectly by means of stochastic modeling based on larger randomized controlled trials (RCTs). However the conduct of RCTs is hampered in an environment such as ours, in which technology is rapidly evolving. As such, there is a relatively limited number of RCTs. Therefore, we investigated as to which extent paired diagnostic studies of accuracy can be also used to shed light on economic implications when considering a new diagnostic test. We propose a simple decision tree model-based cost-utility analysis of a diagnostic test when compared to the current standard procedure and exemplify this approach with published data from lymph node staging of prostate cancer. Average procedure costs were taken from the Danish Diagnosis Related Groups Tariff in 2013 and life expectancy was estimated for an ideal 60 year old patient based on prostate cancer stage and prostatectomy or radiation and chemotherapy. Quality-adjusted life-years (QALYs) were deduced from the literature, and an incremental cost-effectiveness ratio (ICER) was used to compare lymph node dissection with respective histopathological examination (reference standard) and (18)F-fluoromethylcholine positron emission tomography/computed tomography (FCH-PET/CT). Lower bounds of sensitivity and specificity of FCH-PET/CT were established at which the replacement of the reference standard by FCH-PET/CT comes with a trade-off between worse effectiveness and lower costs. Compared to the reference standard in a diagnostic accuracy study, any imperfections in accuracy of a diagnostic test imply that replacing the reference standard generates a loss in effectiveness and utility. We conclude that diagnostic studies of accuracy can be put to a more extensive use, over and above a mere indication of sensitivity and specificity of an imaging test, and that health economic considerations should be undertaken when planning a prospective diagnostic accuracy study. These endeavors will prove especially fruitful when comparing several imaging techniques with one another, or the same imaging technique using different tracers, with an independent reference standard for the evaluation of results.