Final answer:
The correct number of times to invert a light blue tube for coagulation tests is 3 to 4 times, as recommended by the Clinical and Laboratory Standards Institute (CLSI).
Step-by-step explanation:
The light blue tube typically refers to a sodium citrate tube used in medical blood draws for coagulation tests. These tubes must be inverted a specific number of times to mix the anticoagulant with the blood properly without causing hemolysis or clotting. According to the Clinical and Laboratory Standards Institute (CLSI) guidelines, the correct number of times to gently invert a light blue tube is 3 to 4 times. It is important to follow this procedure carefully to ensure the accuracy of coagulation tests such as prothrombin time (PT) and activated partial thromboplastin time (aPTT).
Gentle inversions prevent clotting by mixing the blood with the anticoagulant evenly, and it also avoids the breakdown of blood cells that can happen with vigorous shaking.