To evaluate changes in key hematological parameters and levels of leukocyte inflammatory markers in patients with unstable angina (UA), stratified by post-COVID-19 syndrome status and smoking history.

Materials and methods. A total of 147 patients with UA were included in the study. Group I included 87 patients with post-COVID-19 syndrome, and Group II consisted of 60 patients without post-COVID-19 syndrome. Each group was subdivided by smoking status: IA and IIA (smokers), IB and IIB (non-smokers). The following parameters were assessed in all subgroups: main hematological indicators and leukocyte inflammatory markers: neutrophil/lymphocyte ratio (NLR), monocyte/lymphocyte ratio (MLR), platelet/lymphocyte ratio (PLR), systemic immune inflammation index (SII), systemic inflammation response index (SIRI), and aggregate index of systemic inflammation (AISI).

Results. Mean levels of MLR (37.93 %), SIRI (55.90 %), and AISI (53.99 %) were significantly higher in subgroup IA (smokers with post-COVID-19 syndrome) compared to subgroup IIA (smokers without post-COVID-19 syndrome). In subgroup IA, the proportion of patients exceeding optimal threshold values for MLR, SII, SIRI, and AISI was also 20–35 % significantly higher than in subgroup IIA. Among non-smokers with post-COVID-19 syndrome (subgroup IB), mean levels of NLR, SII, SIRI, and AISI were 33–40 % significantly higher than in subgroup of non-smokers without post-COVID-19 syndrome (subgroup IIB). Additionally, the percentage of individuals exceeding optimal thresholds for NLR, MLR, PLR, SII, and AISI was 20–30 % higher in subgroup IB than in subgroup IIB. The highest mean levels of NLR (50.0 %), MLR (37.9 %), as well as SII, SIRI, and AISI (52–62 %) were observed in subgroup IA compared to subgroup IIB.

Conclusions. Patients with post-COVID-19 syndrome demonstrated significantly higher levels of leukocyte inflammatory markers. In both smoker subgroups (IA and IIA) compared to non-smoker subgroups (IB and IIB), NLR, MLR, SII, SIRI, and AISI levels were significantly elevated by 33–55 %. The most pronounced changes in blood inflammatory markers and the highest proportions of patients exceeding optimal thresholds (NLR, MLR, PLR, SII, SIRI) were recorded in subgroup IA (smokers with post-COVID-19 syndrome).