Is platelet to lymphocyte ratio predictive of preeclampsia? A systematic review and meta-analysis

Figures & data

Figure 1. Selection process of studies included in the review.

Table 1. Studies included in the meta-analysis and their characteristics.

Author (publication year)	Place of study and study design	Subject characteristics	Sample size	Outcomes (compared to controls with no pre-eclampsia)	Newcastle Ottawa quality score
Cui et al. (2023)	China Retrospective/medical registry based	Age similar among three groups; BMI significantly higher in women with mild and severe pre-eclampsia (PE) Gestational age at blood sampling ≥28 weeks	320 (severe – 131; mild – 28; control – 161)	Severe (mean, SD): 103.93 (40.1); 125.25 (42.8) Mild (mean, SD): 109.78 (39.0); 125.25 (42.8)	7
Ozkan et al. (2023)	Turkey Retrospective/hospital medical records	Significantly lower mean age and BMI in the control group; no statistically significant differences with respect to gravidity	1364 (PE – 208; severe – 364; control – 792)	PE (mean, SD): 130.4 (55.7); 132.5 (59.5) Severe (mean, SD): 121.6 (52.9); 132.5 (59.5)	7
Maziashvili et al. (2023)	Georgia Case-control	Majority of the subjects in both groups were in the age range of 26–35 years	126 (PE – 63; control – 63)	PE (mean, SD): 132.0 (42.6); 128.65 (33.4)	7
Madendag et al. (2022)	Turkey Case-control	Maternal age, nulliparity, body mass index, ethnicity, smoking and history of caesarean section were similar among the groups Gestational age at blood sampling was similar in all groups (mean of around 33 weeks)	86 (severe – 28; mild – 28; control – 30)	Severe (mean, SD): 88.2 (47.9); 104.4 (40.0) Mild (mean, SD): 96.2 (36.6); 104.4 (40.0)	8
Elmaradny et al. (2022)	Saudi Arabia Cross-sectional	No statistically significant differences between the two groups according to age, parity, BMI and haemoglobin.	180 (PE – 84; control – 96)	PE (mean, SD): 94.32 (30.8); 138.3 (59.7)	7
Yakiştiran et al. (2022)	Turkey Case-control	Similar maternal age, parity and BMI in both groups; significantly higher gravidity in the PE group	170 (PE – 84; control – 86)	PE (mean, SD): 104.2 (92.3); 71.8 (35.2)	7
Taşkömür and Erten (2021)	Turkey Case-control	Demographic characteristics of the groups in terms of age, height, weight, body mass index (BMI), education, parity and week of birth; Gestational age at blood sampling ≥28 weeks	141 (severe – 14; mild – 48; control – 79)	Severe (mean, SD): 124.9 (32.3); 131.9 (37.2) Mild (mean, SD): 145.0 (34.5); 131.9 (37.2)	8
Bayram and Karaşin (2021)	Turkey Case-control	Similar maternal age, gravidity and BMI between both groups; increased parity in control group	80 (PE – 40; control – 40)	PE (mean, SD): 107.9 (149.9); 128.3 (154.4)	6
Singgih et al. (2021)	Indonesia Cross-sectional	Subjects with mean age of around 30 years and mean gravida of 2.6	924 (PE – 86; control – 838)	PE (mean, SD): 161.6 (82.6); 161.0 (106.4)	6
Gamal El-Din Mahmoud et al. (2021)	Egypt Prospective cohort	Significantly similar maternal age, gravidity, parity and body mass index among the two groups	252 (PE – 37; control – 215)	PE (mean, SD): 70.4 (37.2); 103.3 (39.3)	6
Oğlak et al. (2021)	Turkey Case-control	No significant differences among the groups with respect to maternal age, gravidity, parity and gestational week at the screening	301 (severe – 107; mild – 94; control – 100)	Severe (mean, SD): 138.1 (38.2); 121.1 (27.4) Mild (mean, SD): 137.1 (44.9); 121.1 (27.4)	8
Mannaerts et al. (2019)	Belgium Retrospective	Increased maternal age in control group; increased proportion of nulliparous women in PE group; similar BMI in both groups	197 (PE – 59; control – 138)	PE (mean, SD): 128.9 (50.0); 132.3 (39.7)	7
Gogoi et al. (2019)	India Cross-sectional	No statistically significant differences between groups with respect to maternal age, parity, haemoglobin level, pregnancy duration and socio-economic status	134 (PE – 67; severe – 29; mild – 38; control – 67)	PE (mean, SD): 14.2 (14.4); 9.54 (3.6) Severe (mean, SD): 14.6 (13.2); 9.54 (3.6) Mild (mean, SD): 13.85 (10.2); 9.54 (3.6)	6
Kholief et al. (2019)	Egypt Cross-sectional	All subjects with gestational age ≥34 weeks; maternal morbidity higher in PE group; lower haemoglobin in severe PE group	105 (severe – 35; mild – 35; control – 35)	Severe (mean, SD): 98.4 (59.1); 125.9 (52.4) Mild (mean, SD): 126.4 (61.2); 125.9 (52.4)	7
Syahputra et al. (2019)	Indonesia Case-control	Increased maternal age in PE group; similar BMI in both the groups	140 (PE – 70; control – 70)	PE (mean, SD): 98.8 (116.5); 109.7 (111.9)	6
Örgül et al. (2019)	Turkey Case-control	Similar maternal age, gravidity, parity and BMI in both groups	165 (PE – 42; control – 123)	PE (mean, SD): 128.6 (59.6); 127.8 (58.1)	8
Çintesun et al. (2018)	Turkey Case-control	No statistically significant differences between the two groups in terms of maternal age. Control group women had a higher gravity and parity than the PE group	130 (PE – 64; severe – 13; mild – 51; control – 66)	PE (mean, SD): 129.26 (103.2); 118.1 (126.2) Severe (mean, SD): 207.4 (113); 118.1 (126.2) Mild (mean, SD): 123.95 (85.9); 118.1 (126.2)	7
Sitotaw et al. (2018)	Ethiopia Cross-sectional	No statistically significant differences between the control and PE groups in terms of age, gravidity, parity and gestational weeks	126 (PE – 63; severe – 30; mild – 33; control – 63)	PE (mean, SD): 96.9 (34.0); 108.1 (40.3) Severe (mean, SD): 87.7 (32.5); 108.1 (40.3) Mild (mean, SD): 102.5 (33.5); 108.1 (40.3)	8
Kim et al. (2018)	Republic of Korea Retrospective/hospital medical records	No statistically significant differences among the 3 groups with respect to maternal age, gravidity, number of abortions, and previous history of PE	824 (severe – 227; mild – 126; control – 471)	Severe (mean, SD): 109.1 (4.5); 160.8 (2.9) Mild (mean, SD): 130.3 (4.9); 160.8 (2.9)	8
Yücel and Ustun (2017)	Turkey Retrospective	No statistically significant differences between the groups for maternal age, gravida and parity	219 (severe – 82; mild – 27; control – 110)	Severe (mean, SD): 89.05 (35.3); 102.2 (29.7) Mild (mean, SD): 99.18 (42.4); 102.2 (29.7)	8
Jeon et al. (2017)	Republic of Korea Retrospective/hospital medical records	PE group had higher maternal age and proportion of primipara and shorter gestational period	154 (PE – 68; control – 86)	PE (mean, SD): 119.3 (52.8); 126.8 (36.0)	8
Gezer et al. (2016)	Turkey Retrospective/hospital medical records	Similar age, parity and BMI in the two groups; low haemoglobin in women with PE	430 (PE – 209; control – 221)	PE (mean, SD): 141.9 (51.0); 118.5 (47.2)	6
Toptas et al. (2016)	Turkey Case-control	No statistically significant differences between PE and control for maternal age and gestation at delivery; those with PE had higher parity	187 (PE – 93; severe – 66; mild – 27; control – 94)	PE (mean, SD): 134.4 (64.5); 130.5 (86.2) Severe (mean, SD): 149.8 (67.3); 130.5 (86.2) Mild (mean, SD): 122.9 (92.0); 130.5 (86.2)	8
Kirbas et al. (2015)	Turkey Case-control	Maternal age, gravidity, smoking status and BMI were comparable among all three groups	934 (severe – 326; mild – 288; control – 320)	Severe (mean, SD): 139 (91); 121 (52) Mild (mean, SD): 118 (41); 121 (52)	7
Yavuzcan et al. (2014)	Turkey Retrospective/hospital medical records	Similar age and haemoglobin levels between those with severe PE and healthy controls; gestational age at delivery and birth weight lower in those with severe PE	66 (severe – 30; control – 36)	Severe (mean, SD): 109.81 (55.0); 127.41 (41.2)	7

Figure 2. Weighted mean difference (WMD) of PLR between cases with preeclampsia and healthy controls.

Table 2. Findings of the subgroup analysis between preeclampsia and the healthy controls.

	WMD (95% CI)	N (I^2%)
Country of study
Turkey	10.4 (–2.7 to 23.5)	7 (72.4%)
Others	−11.2 (–23.6 to 1.2)	9 (89.3%)
Total sample size
<200	−3.27 (–13.7 to 7.2)	12 (81.9%)
≥200	−2.5 (–25.7 to 20.6)	4 (93.8%)
Sample size of PE group
<100	−5.5 (–15.7 to 4.7)	14 (84.7%)
≥100	10.6 (–14.4 to 35.6)	2 (93.6%)
Study quality score (NOS)
<7	−2.7 (–19.5 to 14.2)	6 (89.7%)
≥7	−3.3 (–14.7 to 8.1)	10 (81.2%)

Figure 3. Weighted mean difference (WMD) of PLR between cases with mild preeclampsia and healthy controls.

Figure 4. Weighted mean difference (WMD) of PLR between cases with severe preeclampsia and healthy controls.

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Data availability statement

The authors confirm that the data supporting the findings of this study are available within the article and its supplementary materials.