Influence of temperature and relative humidity on patterns formed in dried plasma and serum droplets

In the present methodological study, we investigated the influence of different evaporation conditions upon patterns formed in desiccated plasma and serum droplets; furthermore, we determined the potential of such patterns to distinguish between four donors. Our results show that the development of different pattern features strongly depended on relative humidity: lower relative humidity triggered the formation of cracks, whereas higher relative humidity favored the development of inner crystalline structures. Settings that allowed for the best donor differentiation and at the same time showed high stability of the experimental system were 24.5 ◦C /15% rH and 30.5 ◦C /45% rH for plasma and 30.5 ◦C /15% rH and 36.6 ◦C /45% rH for serum droplets. The results suggest that for the development of diagnostic tests based on pattern formation in evaporating plasma and serum droplets the choice of right evaporation conditions may influence the experimental system stability as also the test accuracy