Which statement is true about capillary specimens compared to venous specimens?

Which statement is true about capillary specimens compared to venous specimens?

• A. Tissue Fluid Contamination
• B. Capillary Specimens Have the Same Analyte Concentrations as Venous Samples
• C. Capillary Specimens Always Fill More Quickly Than Venous Specimens
• D. All Tests Are Validated for Capillary Blood

Answer: (A)

Capillary specimens are more prone to tissue fluid contamination than venous samples because the puncture site is close to the interstitial space and squeezing or excessive milking can push extracellular fluid into the blood drop. This tissue fluid mixes with blood and can dilute or skew the concentrations of many analytes, so capillary results may not reflect venous plasma values. That’s why tissue fluid contamination is a real concern with capillary collection and why careful technique—avoiding squeezing, allowing blood to flow, and discarding the first drop—helps minimize this issue. In contrast, not all tests have validated capillary blood methods, and capillary results aren’t guaranteed to match venous concentrations or fill faster in every case.

Capillary specimens are more prone to tissue fluid contamination than venous samples because the puncture site is close to the interstitial space and squeezing or excessive milking can push extracellular fluid into the blood drop. This tissue fluid mixes with blood and can dilute or skew the concentrations of many analytes, so capillary results may not reflect venous plasma values. That’s why tissue fluid contamination is a real concern with capillary collection and why careful technique—avoiding squeezing, allowing blood to flow, and discarding the first drop—helps minimize this issue. In contrast, not all tests have validated capillary blood methods, and capillary results aren’t guaranteed to match venous concentrations or fill faster in every case.