. 2023 Nov 11;12(22):7044. doi: 10.3390/jcm12227044

Table 1.

Characteristics of included studies (n = 14).

Author, Year, Country	Study Design	STROBE¹⁸ Reporting Guidelines	Age of Participants	No. of Subjects MetS+/MetS−	MetS Criteria	Results
Ahmadzadeh et al., 2017, Iran [21]	Cross-sectional study	19	Men MetS+ 41.4 ± 9.9 MetS− 36.4 ± 9.6	Men 3203/7911 Total 11,114	IDF	Increased WBC (p < 0.001) is related to a higher number of MetS criteria. Men MetS+ 7.2 ± 1.7 (WBC) MetS− 6.7 ± 1.7 (WBC)
Chen et al., 2019, China [22]	Cross-sectional study	20	MetS+ 56.5 ± 0.5 MetS− 47.6 ± 0.4	254/598 Total 852	NCEP ATP III	Elevated WBC levels in MetS+ subjects. MetS+ 7.03 ± 0.1 (WBC) MetS− 6.4 ± 0.06 (WBC)
Chen et al., 2020, China [10]	Cross-sectional study	19	Women MetS+ 60.7 ± 10.0 MetS− 52.6 ± 12.7 Men MetS+ 57.2 ± 10.5 MetS− 54.8 ± 13.5	Women 277/641 Total 918 Men 140/343 Total 483	IDF	Haematological parameters, including WBC and subtypes, correlate with the occurrence of MetS.
Chen et al., 2020, China [10]	Cross-sectional study	19		Women 277/641 Total 918 Men 140/343 Total 483	IDF	Women MetS+ 6.69 ± 1.67 (WBC) MetS− 6.1 ± 1.53 (WBC)		Men MetS+ 7.24 ± 1.66 (WBC) MetS− 6.87 ± 1.59 (WBC)
Hoi et al., 2017, Japan [23]	Cross-sectional study	21	Men MetS+ 49.5 ± 6.5 MetS− 48.8 ± 6.1	Men 251/474 Total 725	NCEP ATP III	Significantly higher white blood cell count in MetS+ subjects. Men MetS+ 6.57 ± 1.55 (WBC) MetS− 5.95 ± 1.44 (WBC)
Li et al., 2019, China [30]	Retrospective cohort study	19	MetS+ 52.5 ± 13.6 MetS− 41.1 ± 13.3	120/1948 Total 2068	Chinese Diabetes Society	The MetS+ group had higher TSH and inflammation levels, indicated by higher WBC, LY, and Mo/HDL.
Li et al., 2019, China [30]	Retrospective cohort study	19	MetS+ 52.5 ± 13.6 MetS− 41.1 ± 13.3	120/1948 Total 2068	Chinese Diabetes Society	MetS+ 7.1 ± 2.11 (WBC) MetS− 6.4 ± 1.6 (WBC) MetS+ 2.57 ± 0.79 (Lymphocyte) MetS− 2.25 ± 0.61 (Lymphocyte)		MetS+ 3.89 ± 1.52 (Neutrophil) MetS− 3.57 ± 1.2 (Neutrophil) MetS+ 0.43 ± 0.15 (Monocyte) MetS− 0.39 ± 0.13 (Monocyte)
Lin et al., 2021, China [9]	Cohort study	20	MetS+ 45 ± 11.6 MetS− 44.9 ± 13.18	179/1363 Total 1542	Chinese Diabetes Society	Subjects with MetS+ have higher levels of leukocytes, neutrophils, and total lymphocytes. Elevated levels of leukocytes, neutrophils, and lymphocytes increased the incidence of MetS.
Lin et al., 2021, China [9]	Cohort study	20	MetS+ 45 ± 11.6 MetS− 44.9 ± 13.18	179/1363 Total 1542	Chinese Diabetes Society	MetS+ 6.6 ± 1.4 (WBC) MetS− 6.21 ± 1.3 (WBC)	MetS+ 3.6 ± 1.03 (Neutrophil) MetS− 3.39 ± 0.94 (Neutrophil)		MetS+ 2.39 ± 0.68 (Lymphocyte) MetS− 2.25 ± 0.56 (Lymphocyte)
Liu C et al., 2019, Taiwan [24]	Cross-sectional study.	19	MetS+ 50.4 ± 11.1 MetS− 45.6 ± 11.1	10,475/23,538 Total 34,013	NCEP ATP III	Inflammatory biomarkers (WBC, CRP, and Hs-CRP), lipid markers (total cholesterol, triglycerides, and LDL-cholesterol), and glycaemic markers (fasting glucose, HbA1c, insulin, HOMA-IR, and SUA) were on average higher in the MetS+ group than in MetS− (p < 0.001). MetS+ 6.83 ± 1.72 (WBC) MetS− 6.05 ± 1.45 (WBC)
Mauss et al., 2020, Germany [25]	Cross-sectional study	19	Men MetS+ 49.5 ± 8.1 MetS− 44.5 ± 9.9	Men 137/552 Total 689	Harmonised criteria	Total leukocyte count and CRP were higher in the MetS+ group, while leukocyte ratios showed no significant differences. Men MetS+ 7.1 ± 1.81 (WBC) MetS− 6.44 ± 1.68 (WBC)
Meng et al., 2017, China [26]	Cross-sectional study	21	MetS+ 52.7 ± 9.7 MetS− 48.9 ± 9.7	2292/4020 Total 6312	Harmonised criteria	They observe that leukocyte, neutrophil, and lymphocyte concentrations are associated with MetS.
Meng et al., 2017, China [26]	Cross-sectional study	21	MetS+ 52.7 ± 9.7 MetS− 48.9 ± 9.7	2292/4020 Total 6312	Harmonised criteria	MetS+ 5.84 ± 1.46 (WBC) MetS− 5.32 ± 1.29 (WBC)	MetS+ 3.29 ± 0.97 (Neutrophil) MetS− 2.98 ± 0.97 (Neutrophil)		MetS+ 1.98 ± 0.49 (Lymphocyte) MetS− 1.77 ± 0.65 (Lymphocyte)
Tanaka et al., 2020, China [31]	Cohort study	19	Women MetS+ 55.2 ± 10.4 MetS− 44.8 ± 9.8 Men MetS+ 50.3 ± 9.4 MetS− 44.8 ± 9.7	Women 401/8035 Total 8436 Men 1184/10,542 Total 11,726	NCEP ATP III	Higher levels of WBC are observed in the MetS group.
Tanaka et al., 2020, China [31]	Cohort study	19		Women 401/8035 Total 8436 Men 1184/10,542 Total 11,726	NCEP ATP III	Women MetS+ 6.0 ± 1.5 (WBC) MetS− 5.3 ± 1.4 (WBC)		Men MetS+ 6.6 ± 1.7 (WBC) MetS− 5.7 ± 1.5 (WBC)
Uslu et al., 2018, Turkey [32]	Case–control study	19	MetS+ 47 ± 13.5 MetS− 44 ± 15.2	147/134 Total 281	NCEP ATP III	MHR is a useful inflammatory marker to assess MetS and disease severity.
Uslu et al., 2018, Turkey [32]	Case–control study	19	MetS+ 47 ± 13.5 MetS− 44 ± 15.2	147/134 Total 281	NCEP ATP III	MetS+ 7.96 ± 2.63 (WBC) MetS− 6.69 ± 1.58 (WBC)		MetS+ 0.59 ± 0.26 (Monocyte) MetS− 0.48 ± 0.16 (Monocyte)
Vahit et al., 2017, Turkey [27]	Cross-sectional study	20	MetS + 57.4 ± 8.8 MetS− 56.3 ± 9.1	371/391 Total 762	NCEP ATP III	MRLs such as MHR may be novel and valuable indicators in MetS.
Vahit et al., 2017, Turkey [27]	Cross-sectional study	20	MetS + 57.4 ± 8.8 MetS− 56.3 ± 9.1	371/391 Total 762	NCEP ATP III	MetS+ 7.55 ± 1.66 (WBC) MetS− 7.49 ± 1.69 (WBC)		MetS + 4.32 ± 1.34 (Neutrophil) MetS− 4.51± 1.36 (Neutrophil)
Xie et al., 2021, China. [28]	Cross-sectional study	19	MetS+ 26.1 MetS− 25.7	655/2189 Total 2844	IDF	Lasso’s logistic regression algorithm helped to identify MetS with high accuracy in an occupational population.
Xie et al., 2021, China. [28]	Cross-sectional study	19	MetS+ 26.1 MetS− 25.7	655/2189 Total 2844	IDF	MetS+ 7.37 ± 1.79 (WBC) MetS− 6.68 ± 1.65 (WBC) MetS+ 0.42 ± 0.15 (Monocyte) MetS− 0.39 ± 0.13 (Monocyte) MetS+ 0.17 ± 0.13 (Eosinophil) MetS− 0.18 ± 0.18 (Eosinophil)		MetS+ 2.45 ± 0.69 (Lymphocytes) MetS− 2.39 ± 0.71 (Lymphocytes) MetS+ 4.32 ± 1.42 (Neutrophil) MetS− 3.71 ± 1.25 (Neutrophil) MetS+ 0.07 ± 0.16 (Basophil) MetS− 0.05 ± 0.11 (Basophil)
Yang et al., 2020, China. [29]	Cross-sectional study	19	≥60 years	Women 608/1771 Total 2379 Men 311/1889 Total 2200	NCEP ATP III	They observe interactions between leukocytes, monocytes, neutrophils, and sex in MetS.
Yang et al., 2020, China. [29]	Cross-sectional study	19	≥60 years	Women 608/1771 Total 2379 Men 311/1889 Total 2200	NCEP ATP III	Women MetS+ 5.68 ± 1.31 (WBC) MetS− 5.15 ± 1.28 (WBC) MetS+ 1.8 ± 0.57 (Lymphocytes) MetS− 1.61 ± 0.51 (Lymphocytes) MetS+ 0.3 ± 0.1 (Monocyte) MetS− 0.28 ± 0.1 (Monocyte) MetS+ 3.41 ± 0.99 (Neutrophil) MetS− 3.1 ± 1.01 (Neutrophil) MetS+ 0.13 ± 0.11 (Eosinophil) MetS− 0.13 ± 0.13 (Eosinophil) MetS+ 0.03 ± 0.02 (Basophil) MetS− 0.03 ± 0.02 (Basophil)		Men MetS+ 5.87 ± 1.43 (WBC) MetS− 5.48 ± 1.53 (WBC) MetS+ 1.75 ± 0.53 (Lymphocytes) MetS− 1.56 ± 0.62 (Lymphocytes) MetS+ 0.35 ± 0.16 (Monocyte) MetS− 0.34 ± 0.13 (Monocyte) MetS+ 3.56 ± 1.14 (Neutrophil) MetS− 3.4 ± 1.21 (Neutrophil) MetS+ 0.16 ± 0.15 (Eosinophil) MetS− 0.14 ± 0.14 (Eosinophil) MetS+ 0.04 ± 0.02 (Basophil) MetS− 0.03 ± 0.02 (Basophil)

CRP, C-reactive protein; HbA1c, haemoglobin A1c; HOMA-IR, Homeostatic Model Assessment of Insulin Resistance; hsCRP, high-sensitivity C-reactive protein; IDF, International Diabetes Federation; LY, lymphocytes; LMR, lymphocyte-to-monocyte ratio, MetS, metabolic syndrome; MHR, monocyte to high-density lipoprotein cholesterol ratio; Mo/HDL, monocyte/high-density lipoprotein; NCEP ATP III, National Cholesterol Education Program Adult Treatment Panel III; STROBE, Strengthening the Reporting of Observational Studies in Epidemiology; SUA, serum uric acid; TSH, thyroid-stimulating hormone; WBC, white blood cells.