POSTN and Stroke: Furthermore, the increase in periostin levels observed from day 1 to the 4th week was correlated with the NIHSS scores on day 1 (r = 0.505; p < 0.001, Fig. 2C) and day 6 (r = 0.450, p = 0.002, Fig. 2D), along with the stroke volume (r = 0.352, p = 0.022).