Quality of plasma sampled by different methods for multiple blood sampling in XXXX .

@entity19 @entity413
For oral @entity413 tolerance test (OGTT) in @entity19 , multiple blood samples need to be taken within a few hours from conscious @entity19 . Today, a number of essential parameters may be analysed on very small amounts of plasma, thus reducing the number of animals to be used. It is, however, crucial to obtain high-quality plasma or serum in order to avoid increased data variation and thereby increased group sizes. The aim of this study was to find the most valid and reproducible method for withdrawal of blood samples when performing OGTT. Four methods, i.e. amputation of the tail tip, lateral tail incision, puncture of the tail tip and periorbital puncture, were selected for testing at 21 degrees C and 30 degrees C after a pilot study. For each method, four blood samples were drawn from C57BL/6 @entity19 at 30 min intervals. The presence of clots was registered, haemolysis was monitored spectrophotometrically at 430 nm, and it was noted whether it was possible to achieve 30-50 microL blood. Furthermore, a small amount of extra blood was sampled before and after the four samplings for testing of whether the sampling induced a blood @entity413 change over the 90 min test period. All methods resulted in acceptable amounts of plasma. Clots were observed in a sparse number of samples with no significant differences between the methods. Periorbital puncture did not lead to any haemolysed samples at all, and lateral tail incision resulted in only a few haemolysed samples, while puncture or amputation of the tail tip induced haemolysis in a significant number of samples. All methods, except for puncture of the tail tip, influenced blood @entity413 . Periorbital puncture resulted in a dramatic increase in blood @entity413 of up to 3.5 mmol/L indicating that it is stressful. Although lateral tail incision also had some impact on blood @entity413 , it seems to be the method of choice for OGTT, as it is likely to produce a clot-free non-haemolysed sample, while periorbital sampling, although producing a high quality of sample, induces such a dramatic change in blood @entity413 that it should not be applied for OGTT in @entity19 .
