Assessment of Dried Plasma Spots (DPS) as an Appropriate Sample Matrix for the Measurement of Circulating Calretinin, a Biomarker for Mesothelioma-A Proof-Of-Concept Study

Our plain-English summary of Assessment of Dried Plasma Spots (DPS) as an Appropriate Sample Matrix for the Measurement of Circulating Calretinin, a Biomarker for Mesothelioma-A Proof-Of-Concept Study, by J. Gleichenhagen, N. Kaiser, T. Brüning, et al (Journal of Clinical Laboratory Analysis, 2026).

The study

• Authors: J. Gleichenhagen, N. Kaiser, T. Brüning, G. Johnen, D.G. Weber
• Journal: Journal of Clinical Laboratory Analysis
• Published: 2026;40(11):e70271
• Read it: PubMed · Publisher · Free full text

Abstract

Background: Microsampling using filter cards for dried blood spots (DBS) and dried plasma spots (DPS) is a well-established technique offering practical advantages for blood collection and subsequent processing. For DBS/DPS, only a small sample volume is required it enables transport and storage at ambient temperature, and it is well suited for decentralized sample collections and resource-limited settings, as well as collection from elderly individuals, when venous blood collection might be problematic. Many protein-based biomarker assays like enzyme-linked immunosorbent assays (ELISA) depend on blood, plasma, or serum as sample matrix. Calretinin is an established biomarker for the early detection of mesothelioma. Herein, we investigated whether DPS are suitable for the determination of calretinin protein by ELISA in comparison to commonly used plasma samples.

Methods: Plasma samples of 47 mesothelioma patients and 47 matched asbestos-exposed controls were spotted onto filter cards. After drying, calretinin was reconstituted and determined using ELISA.

Results: It was revealed that the use of filter cards, i.e., DPS as sample matrix, was comparable to and in good agreement with the use of plasma. Calretinin could be determined reliably and comparably even after storage for 5 days at ambient temperature. Additionally, the performance of calretinin as biomarker using DPS is improved in comparison to the use of plasma, resulting in a slightly increased sensitivity at constant specificity.

Conclusion: The findings of this proof-of-concept study suggest that filter cards represent a valuable alternative sampling method to determine calretinin for the detection or monitoring of mesothelioma.

© 2026 The Author(s). Journal of Clinical Laboratory Analysis published by Wiley Periodicals LLC.

In plain English

This proof-of-concept laboratory study from Germany tested whether calretinin, a blood protein used as a marker for mesothelioma, could be measured from plasma dried on filter cards (dried plasma spots) as well as from liquid plasma. The authors used stored plasma from 47 mesothelioma patients and 47 matched asbestos-exposed controls, collected between December 2008 and March 2018. With dried spots, 30 of 47 patients had calretinin at or above the 0.6 ng/mL cutoff and no control did. That gave a sensitivity of 64% (95% CI: 52%–78%) and a specificity of 100%. With liquid plasma, sensitivity was 62%, and one control was slightly above the cutoff (0.63 ng/mL). The authors noted that the difference in sensitivity was driven by only two samples. Dried spots gave somewhat higher values above 1 ng/mL. After five days of storage at ambient temperature, three patients' samples dropped below the cutoff. The authors concluded that dried plasma spots are a reliable sample type for calretinin. They noted the small sample size, and that blood still had to be centrifuged to obtain plasma.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Proof-of-concept laboratory method-comparison study: the same stored plasma samples were measured as liquid plasma and as dried plasma spots on filter cards, using a calretinin ELISA
• Who was studied: 47 mesothelioma patients (38 epithelioid, 5 biphasic, 4 sarcomatoid; median age 73) and 47 matched asbestos-exposed controls, Germany (Ruhr University Bochum ethics approval); samples collected December 2008 to March 2018
• Exposure: The controls are described only as asbestos-exposed; the article gives no fiber types, jobs or doses. The comparison studied was the sample type: dried plasma spots versus liquid plasma.
• Main results:
  • Dried plasma spots: calretinin was above the limit of quantification in 47 of 94 samples (35 mesothelioma patients, 12 controls)
  • Dried plasma spots: 30 of 47 mesothelioma patients were at or above the 0.6 ng/mL cutoff; all controls were below it (two near it, at 0.51 and 0.57 ng/mL)
  • Dried plasma spots at the 0.6 ng/mL cutoff: sensitivity 64% (95% CI: 52%–78%), specificity 100%; the statistically optimal cutoff of 0.56 ng/mL gave 66% sensitivity and 100% specificity
  • Liquid plasma: 28 mesothelioma patients had values above 0.6 ng/mL, and one control was slightly above the cutoff (0.63 ng/mL)
  • Sensitivity in ROC analysis was 64% with dried plasma spots and 62% with liquid plasma; the authors stated the difference was driven by only two samples
  • Dried plasma spots gave higher calretinin values than plasma at concentrations above 1 ng/mL (Bland–Altman bias of −0.29)
  • After 5 days' storage at ambient temperature, values stayed comparable to plasma values, but three mesothelioma patients' samples dropped below the cutoff
• The authors' conclusion: The authors concluded that dried plasma spots are a reliable sample matrix for measuring calretinin, and may support simpler sample collection for detecting and monitoring mesothelioma
• Limitations the authors state:
  • Relatively small sample size; larger studies are needed to verify the findings
  • The difference in sensitivity between the two methods was driven by only two samples
  • The method still requires centrifuging whole blood to obtain plasma
  • The cutoff value may need adjusting when switching from plasma to dried spots and with longer storage

Topics

The National Library of Medicine indexes this study under subjects our site covers: Mesothelioma.

Medical terms in this study, explained in our Lexicon: Calretinin, Biomarker, Mesothelioma.

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