Which laboratory tests should NOT be performed via capillary puncture?

Capillary puncture is a common method for collecting blood, especially for small volumes needed in certain tests. However, there are specific types of laboratory tests that should be avoided when using this method due to concerns about the integrity and accuracy of the results.

Blood cultures require a larger volume of blood to ensure that any potential microbial growth can be accurately detected. Capillary samples can often lead to contamination because of the presence of skin flora, and the smaller volume may not provide enough material to support proper microbial growth.

Most erythrocyte sedimentation rate methods typically require venous blood as they depend on precise measurements of sedimentation, which can be influenced by variations in capillary blood composition, such as the presence of interstitial fluid or the altered ratios of blood components in capillary samples.

Coagulation studies that specifically need a plasma specimen also do not lend themselves well to capillary puncture, as the small amount of blood may not provide adequate plasma for testing. Coagulation tests require a certain volume and quality of plasma to ensure accurate results, and capillary samples can lead to inaccuracies.

Considering these factors, it is clear that capillary puncture should not be employed for blood cultures, most erythrocyte sedimentation rate methods, and