PIK3C2A and interstitial lung disease: Furthermore, serological biomarkers were not significantly different between ILD patients with and without post-COVID-19 dyspnea, except for CPK levels (p = 0.025, Table 4): CPK levels were significantly higher (mean difference: 34.8, 95%CI 5.2 to 64.4) in ILD patients who developed post-COVID-19 dyspnea when compared with those without post-COVID-19 fatigue (Table 4).