Which of the following tests has a fasting requirement?

Choice A reason:

Performing a heel stick on a 5-year-old patient is not an appropriate technique. Heel sticks are typically used for infants, particularly newborns, to minimize discomfort and because their finger pads may not be fully developed for finger sticks. By the age of 5, a child's veins are usually developed enough for venipuncture, which is the preferred method.

Choice B reason:

Performing a finger stick on a toddler patient is an appropriate technique for specimen collection. This method is commonly used for children who are not yet old enough for venipuncture but have outgrown the heel stick method. The finger stick is performed on the palmar surface of the distal phalanx, usually of the middle or ring finger, and is considered safe and effective for collecting small blood samples in toddlers.

Choice C reason:

Performing a thumb stick on an infant is not an appropriate technique. The thumb has a pulse and is more sensitive, which can cause unnecessary pain and distress to the infant. Additionally, the thumb's size and increased movement make it a less suitable site for specimen collection in infants.

Choice D reason:

Performing a thumb stick on a 5-year-old patient is also not an appropriate technique. As with infants, the thumb's sensitivity and the presence of a pulse make it a less desirable site for blood collection. For a 5-year-old, venipuncture or a finger stick on a non-thumb finger would be more appropriate and less distressing.

Choice A Reason:
Inverting the tube 5 to 7 times may not be sufficient to mix the blood thoroughly with the EDTA. This could lead to partial clotting and potentially inaccurate test results. The EDTA anticoagulant works by binding calcium ions, which are necessary for blood clotting. Without adequate mixing, the EDTA may not be evenly distributed, leaving some areas of the blood sample able to clot.

Choice B Reason:
Inverting the tube only 2 to 4 times is inadequate for proper mixing. This minimal agitation would likely result in clot formation because the anticoagulant would not be sufficiently mixed with the blood. Clots can interfere with the accuracy of hematological tests by trapping cells and altering the specimen's composition.

Choice C Reason:
Inverting the tube 1 to 3 times is clearly insufficient and would almost certainly lead to clotting. The purpose of inverting the tube is to ensure that the EDTA coats all the blood cells, preventing coagulation. Such a low number of inversions would not allow for the anticoagulant to perform its function effectively.

Choice D Reason:
Inverting the tube 8 to 10 times is the recommended practice. This number of inversions ensures that the blood is fully mixed with the EDTA, preventing clot formation and preserving the integrity of the sample for accurate laboratory analysis. It is important to perform these inversions gently to avoid hemolysis, which can also affect test results. Hemolysis occurs when red blood cells are damaged and their contents leak out, which can happen if the blood is shaken too vigorously.