PF4 and essential thrombocythemia: The results show that the serum GPIbα, SELP, PF4, MMP1, and FLNA protein levels were significantly lower than those in healthy subjects, with significant differences (p < 0.0001), and the COL1A1 levels were lower in ET patients than in healthy controls, although there were no statistically significant changes (see Table 2 for particular results).