Are The Neutrophil-to-lymphocyte, Platelet-to-lymphocyte And Monocyte-to-lymphocyte Ratios Predictive Factors For The Retinopathy Of Prematurity?

Purpose: In this study, we aimed to evaluate the possible relationship between the neutrophil-to-lymphocyte, monocyte-to-lymphocyte and platelet-to-lymphocyte ratio and retinopathy of prematurity (ROP). Method: The data of 348 patients who applied to Erzincan University Ophthalmology Unit for screening the retinopathy of prematurity were analyzed retrospectively. One hundred sixty seven patients who were collected CBC samples within the first 72 hours after delivery and who met the inclusion criteria were included in the study. Infants with a gestational age of ≤35 week were screened for ROP. Pateints were divided into two groups. Group 1 was involved the patients with the diagnosis of ROP and group 2 was involved the normal patients (no ROP). The levels of NLR, PLR and MLR were determined in two groups. Results: Fifty nine patients who were detected ROP are in group 1 and 108 patients who were not seen ROP are in group 2 in the study. The mean gestational age at birth of the patients was 30,4 ± 2,1 [26-34] weeks in group 1 and 33,7 ± 1,7 [27-35] weeks in group 2.( P =0.004) The mean gestational weigth at birth was 1927,2 ± 158,4 [1690-2300] gram in group 1 and 2169,1 ± 283,1 [1750-3100] gram in group 2. ( P <0.001) With the result of logistic regression analysis, gestational age [Odds Ratio(OR): 0.531, 95%CI: 0.388-0.726, P <0.001], NLR [OR:34.849, 95%CI: 2.091-580.779, P :0.013] and PLR [OR: 1.067, 95%CI: 1.034-1.110, P <0.001] were detected the independent risk factors for ROP. Conclusion: Our study revealed that higher NLR and PLR which are evaluated with in first 72h after birth is an independent predictor of ROP.

gestational age of ≤35 week were screened for ROP. Pateints were divided into two groups. Group 1 was involved the patients with the diagnosis of ROP and group 2 was involved the normal patients (no ROP). The levels of NLR, PLR and MLR were determined in two groups.

Clinical evaluation:
Infants with a smaller gestational age than 35 weeks were examined for ROP after administering tropicamide 1% (Tropamid ® , Bilimilaç ® ,Gebze, Turkey) eye drops and phenylephrine hydrochloride 0.5% (Mydfrin ® , Alcon ® , Fort Worth, TX) eye drops for three times for pupillary dilatation. The ROP examination was performed by the same experienced eye professional using a binocular indirect ophthalmoscope combined with a sclera depressor after administering proparacaine hydrochloride 0.5% (Alcaine ® , Alcon ® , Fort Worth, TX)eye drops as the topical anesthetic. The ROP status was graded according to the international classification of ROP in all infants. The ROP status was noted including the stage, zone and extent of the disease, and the presence or absence of plus disease for each infant. 12 Each infant was also graded according to the maximum stage of ROP examined in either eye.
All blood samples were gathered and investigated within the first 72 h after birth.

Exclusion criteria:
Infants born with hematologic disorders, received postnatal steroid therapy or a blood product transfusion before the ROP examination were excluded from the study. And also patients with respiratory distress syndrome (RDS), asphyxia neonatorum, neonatal pneumonia, premature rupture of membranes (PROM), necrotizing enterocolitis, hypoxicischemic encephalopathy (HIE) and blood culture-proven sepsis were excluded from the study. Infants who did not attend follow-up regularly and who had any other accompanying ocular or systemic diseases were excluded from the study.

Statistical analysis:
The

Results
In Group 1, 34 patients of the 59 patients were male and 25 were female. In Group 2, 68 of the 108 patients were male and 40 were female. There wasn't any statistically significant difference between the two groups in terms of gender distribution (P = 0.745). The CBC test results of the patients are shown in Table 1.
When the CBC test results of the patients were evaluated, the mean neutrophil count was 3.74 ± 1.85 (10 9 /L) in Group 1 and 1.91 ± 0.87 (10 9 /L) in Group 2. The difference in the neutrophil count between the two groups was statistically significant (P < 0.001). The average lymphocyte count was 4.86 ± 1.56 (10 9 /L) in Group 1 and 5.22 ± 1.58 (10 9 /L) in Group 2. There wasn't any statistically significant difference between the two groups in terms of the lymphocyte count (P = 0.394). The mean monocyte count was 1.43 ± 0.49 (10 9 /L) in Group 1 and 0.86 ± 0.46 (10 9 /L) in Group 2, with no significant difference between the two (P = 0.088). The average platelet count was 453.36 ± 121.96 (10 9 /L) and 304.33 ± 117.58 (10 9 /L) in Groups 1 and 2, respectively, and the difference was not statistically significant (P = 0.744).

Discussion
It is certain that systemic inflammatory responses of maternal immune system and vigorous neonatal inflammatory reactions play a significant role in the development of ROP. [12][13][14][15] Systemic inflammatory responses may affect the creation of abnormal retinal vascularization and promote the risk of ROP, independent of gestational age and weight or intensity of early systemic disease. 16 Woo et al.also informed that umbilical cord blood cytokine levels and perinatal factors were significantly associated with the pathogenesis of ROP. 17 NLR, PLR or MLR have been used in the prognostic diagnosis of cancer in many different branches of medicine and clinically significant results have been obtained. [18][19][20][21] Previous studies indicated that increased neutrophil count and decreased lymphocyte count were associated with a systemic inflammatory response and physiological stress, respectively. [22][23][24][25] In our study, the neutrophil count was meaningfully higher in the ROP group, but the logistic regression analysis indicated that the neutrophil count was not an independent risk factor for ROP. No significant difference was observed between the lymphocyte values of the groups with and without ROP. In the logistic regression analysis, the lymphocyte count was not associated with ROP, as in the neutrophil count. Similarly, the number of monocytes was not associated with ROP.
Guida et al. found a relationship between sepsis and thrombocytopenia in babies with a very low birth weight, and they suggested that the pathogens that caused sepsis might affect the platelet kinetics. 26 In our study, no relationship was found between the presence of ROP and platelet count, and the exclusion of the infants with systemic problems, such as sepsis may have been effective in the emergence of this condition.
Several studies have shown that the NLR, PLR and MLR values, which are related to systemic inflammation, may be prognostic factors for ocular diseases, such as degenerative myopia, keratoconus and age-related macular degeneration. [27][28][29] Kurtul et al. examined the relationship between ROP and NLR and found no independent risk relationship. 3 The authors only observed a relationship between the lymphocyte count and ROP. In the current study, the logistic regression analysis showed that PLR and NLR were independent risk factors for ROP. In addition, in the ROC analysis, the cut-off value was found to be 0.53 for NLR and 81.48 for PLR; however, no relationship was found between the lymphocyte count and ROP, unlike the results reported by Kurtul et al.
The major limitation of our study is that severe ROP cases were not included in the sample. Some postnatal conditions, such as oxygen support, intraventricular hemorrhage, anemia, apnea, and sepsis have been shown to be associated with ROP progression. 30 These accompanying pathologies are likely to affect the NLR, PLR and MLR values.
Accordingly, the patients with severe ROP were excluded from the study group. In

Consent for publication
Not applicable.

Availability of data and materials
All generated or analyzed data during this study are included in the supporting file.

Competing interests
In accordance with our ethical obligation as a researcher, all authors are reporting that we Funding: This study was not funded.

Authors' contributions
AU and Eİ conceived and supervised this research. AU, NGT and HY collected and analyzed the data in the study. AU wrote the initial manuscript, revised by TU and YK. All authors critically reviewed the manuscript for significant intellectual content and approved the final version.