Comparing Vitamin D Results and Acceptability of Sampling Obtained From Dried Blood Spot, Tasso+ Capillary Sampling, and Venous Blood.

This study will evaluate the performance and acceptability of different sampling methods for measuring vitamin D, specifically 25-hydroxyvitamin D₂ and 25-hydroxyvitamin D₃. It will compare results obtained from the routine self-collected dried blood spot (DBS) cards currently in use in our laboratory, with paired capillary and venous serum samples. This compares the collection using three approaches: finger-prick DBS, venepuncture, and the CE-marked Tasso+ upper-arm self-sampling device. The study aims to assess both quantitative agreement between sample types and user acceptability of each collection method.

Inclusion criteria

• Adults aged 18 years or older.
• Current healthcare staff or staff volunteers.
• Already consented to use the routine dried blood spot (DBS) vitamin D service.
• Able and willing to provide all three sample types- routine DBS finger-prick sample, a Tasso+ upper-arm self-collected capillary sample, and a venous blood sample taken by a trained Trust phlebotomist.
• Able to give informed consent.
• Able to complete a short questionnaire in English.

Exclusion criteria

• • Participants will not be able to take part if any of the following apply:

• Under 18 years of age
• Not a member of staff or staff volunteer
• Known difficulty with blood sampling, such as a history of fainting, severe needle phobia, or conditions that make venepuncture unsafe.
• Skin conditions or injuries on the upper arm that would prevent safe use of the Tasso+ device.
• Bleeding disorders or current use of anticoagulant medication that would make capillary or venous sampling unsafe.
• Inability to give informed consent, including difficulty understanding the study information.
• Inability to complete the short questionnaire in English, as this is needed to assess user experience.