key: cord-0769784-sks8rdxg authors: Sayed, Anwar A.; Allam, Assem A.; Sayed, Ayman I.; Alraey, Mohammed A.; Joseph, Mercy V. title: The use of neutrophil-to-lymphocyte ratio (NLR) as a marker for COVID-19 infection in Saudi Arabia: A case-control retrospective multicenter study date: 2021-04-03 journal: Saudi Med J DOI: 10.15537/smj.2021.42.4.20200818 sha: 7dd3d40731f00d5eb10b21b2616f4cc79c77a174 doc_id: 769784 cord_uid: sks8rdxg OBJECTIVES: To assess the neutrophil-to-lymphocyte ratio (NLR) diagnostic and prognostic value in the context of Coronavirus disease-2019 (COVID-19) infection in Saudi Arabia. METHODS: A case-control study in which 701 confirmed COVID-19 patients (of which 41 were intensive care unit [ICU]-admitted) and 250 control subjects were enrolled. The study was conducted retrospectively in October on patients admitted to 3 separate hospitals in Saudi Arabia namely: King Abdullah Bin Abdulaziz University Hospital (Riyadh), Ohud Hospital (Madinah), and Nojood Medical Center (Madinah) between May and September 2020. Neutrophil-to-lymphocyte ratio was calculated based on absolute neutrophil and lymphocyte count. Institutional ethical approval was obtained prior to the study. RESULTS: Patients (median age 35 years), of which 54.8% were females, were younger than the control cohort (median age 48 years). Patients had significantly higher NLR compared to the control group. Intensive care unit admitted patients had significantly higher platelet, WBC and neutrophil counts. The ICU patients’ NLR was almost twice as of the non-intensive patients. The NLR value of 5.5 was found to be of high specificity (96.4%) and positive predictive value (91.4%) in diagnosing COVID-19. Furthermore, it had a very good sensitivity (86.4%) in predicting severe forms of disease, such as, ICU admission. CONCLUSION: Neutrophil-to-lymphocyte ratio is an important tool in determining the COVID-19 clinical status. This study further confirms the prognostic value of NLR in detecting severe infection, and those patients with high NLR should be closely monitored and managed. T he novel coronavirus disease-2019 )COVID-19( global pandemic has resulted in efforts of researchers and governments being devoted to understanding this novel infection and how to prevent its spread. Gaining insights on the infection and understanding its effect on the body and the immune system will allow for the development of precise diagnostic assays for COVID- 19 . Although it was first described as a respiratory disease; however, up to 20% of COVID-19 patients experience severe infection with severe extra-pulmonary manifestations including coagulopathy and septic shock. 1 These manifestations are often unexpected, rapid, and fatal if not managed urgently in an intensive care unit )ICU(. 2 Additionally, COVID-19 patients had significantly high levels of pro-inflammatory cytokines, secondary to excessive immune response, and is often referred to as a "cytokine storm". 3, 4 Such findings further support the systematic nature of the infection and hence developing diagnostic and prognostic tools should not focus solely on the respiratory system. These developed diagnostic tools varied in their detecting mechanism. Several diagnostic assays have been developed which are based on detecting anti-COVID-19 immunoglobulin, as well as assays that detect viral particles, such as, quantitative and real-time polymerase chain reaction )PCR(. So far, the PCR methods remain the most reliable and accepted method of diagnosis for COVID-19 infection. 5 Several independent risk factors have been determined to yield poorer outcomes when present among patients with COVID-19, including older ages, obesity and the presence of comorbidities, such as diabetes mellitus. 6 It has been suggested that neutrophilto-lymphocyte ratio )NLR( carries a prognostic value in a variety of conditions including, but not limited to, acute respiratory distress syndrome, solid tumors and sepsis. [7] [8] [9] Additionally, studies have suggested that NLR is an independent prognostic indicator for the severity of COVID-19 infection. 10 However, the importance of NLR, in regard to the COVID-19 infection, as a diagnostic, such as, to differentiate from those who are not infected, and prognostic tool remains to be determined in Saudi Arabia. This study aims to assess the value of NLR as a diagnostic tool, in a cohort of patients with COVID-19 in Saudi Arabia, and its usefulness in predicting poorer outcomes. Methods. Nine hundred fifty-one participants were included in this study from 3 separate hospitals in Saudi Arabia namely: King Abdullah Bin Abdulaziz University Hospital )Riyadh(, Ohud Hospital )Madinah( and Nojood Medical Center )Madinah(. There were 701 patients admitted for a suspected COVID-19 infection, and diagnosis was confirmed by quantitative PCR )qPCR( on collected nasopharyngeal swab. The inclusion criteria for this study are in line with the Saudi Ministry of Health criteria for hospital admission of COVID-19 patients v1.1, 11 which are as follows: confirmed cases by qPCR, symptomatic, low oxygen saturation <94% on room air and clinical or radiological evidence of pneumonia. Patients with other criteria indicating admission such as the use of biological immunosuppressants, active malignancy or history of organ transplant were excluded from this study. Out of these 701 patients, 41 patients were admitted to the ICU. Intensive care unit admission criteria were as follows: a temperature of 38.5°C accompanied with a decrease in mean arterial pressure below 60 mmHg or shortness of breath that is New York Heart Association )NYHA( class III or higher which is characterized as "marked limitation in activity due to symptoms, even during less-than-ordinary activity, example: walking short distances )20-100 m(. Comfortable only at rest." 12 The remaining 250 subjects served as COVID-19free control subjects who were admitted for an elective surgical procedure and tested negative for COVID-19 using qPCR diagnostic test. A multicenter case-control cross-sectional study in which patients' clinical data were anonymously collected. This study was conducted in October retrospectively on patients admitted between May and September 2020. Collected data included patients' gender, age and complete blood count results with white blood cell )WBC( differentials. No personal or identification information were collected in this study. This study was conducted after obtaining the ethical approval no. 005-1442 from the Taibah Our cohort of patients had a median red blood cells )RBC( count of 4.75 x 10 6 /L which was significantly lower compared to the control group )p<0.0001(. Although the median hematological values of the COVID-19 patients did not suggest an anemic profile, patients had significantly lower hemoglobin levels, mean corpuscular volume )MCV( and mean corpuscular hemoglobin )MCH( compared to the control cohort )p<0.0001(. Furthermore, COVID-19 patients had significantly lower platelet count compared to the control group )231.5 versus [vs] 309.5 x 10 3 /µl; p<0.0001(. Upon examining the differential )WBC( profile, many differences were observed between the COVID-19 cohort and the control group. Patients with COVID-19, in comparison to the control group, had significantly lower WBC indices, including total WBC count )5.5 vs 7.2 x 10 3 /µl(, neutrophil count )3.48 vs 4.4 x 10 3 /µl(, lymphocyte count )0.9 vs 2.1 x 10 3 /µl( and monocyte count )0.33 vs 0.6(. All these differences were statistically significant )p<0.0001(. However, COVID-19 patients had significantly higher neutrophil percentages compared to the control cohort )66.8 vs 58%; p<0.0001(. Despite the lower WBC indices in COVID-19 patients, the calculated NLR was significantly higher compared to the control group )2.9 vs 2.18; p<0.0001( as shown in Figure 1 . To examine whether the NLR correlated with any of the patients' biological variables, multiple linear regression analysis was performed. Expectedly, Out of these ICU patients, 22 patients were male )53.7%( while the remaining 46.3% were female. Their median age was 45 years old )95% CI 36.51-52.47(, which was significantly higher than the non-intensive ICU patients )45 vs 35 years old; p=0.0062(. Kruskal Wallis analysis of the multiple variables of ICU patients compared to the non-intensive COVID-19 patients and the control group yielded many observed differences. Statistically significant differences were observed in the RBC indices as well as the platelet count )p<0.0001(. In fact, the median platelet count of ICU patients was significantly higher compared to non-intensive patients )249 vs 230 x10 3 /µl; p<0.05(. However, both patient cohorts, non-intensive and ICU, had significantly lower platelet count compared to the control cohort )230 and 249 vs 309.5 x10 3 /µl; p<0.0001(. Table 2 -Clinical characteristics and laboratory results of the control and both patients' cohorts )non-intensive and intensive care unit [ICU]-admitted( Covid-19 patients. Significant differences were observed in the WBC indices between the control and 2 patients' cohorts. There were significant differences in the total WBC, as well as other indices such as, neutrophil and lymphocyte counts and percentages and NLR. Compared to non-intensive patients, ICU patients had significantly higher WBC count )6.96 vs 5.37 x10 3 /µl; p<0.0008(, higher neutrophil count )4.6 vs 3.39 x10 3 /µl; p<0.0043( and lower lymphocyte count, although not significantly )1 vs 1.2 x10 3 /µl; p=0.05(. Furthermore, ICU patients had significantly higher NLR, almost as twice as nonintensive patients )5.5 vs 2.85; p=0.0014( as shown in To examine whether the NLR correlated with any of the ICU patients' biological variables, multiple linear regression analysis was performed. Similar to non-intensive patients, lymphocytic count significantly correlated with NLR )p<0.0001(. Noticeably, a positive correlation was observed between NLR and the MCV among ICU patients )p<0.05(. An overall analysis of the total patients' cohort has yielded an NLR value of 5.5 which has been tested. An NLR value of 5.5 seemed to be of very low sensitivity in detecting cases of COVID-19, as compared to the control group, with sensitivity of 23.65%. However, this value yielded a high positive prognostic value at 91.43% and a very high specificity at 96.4%. In other words, a person with an NLR of 5.5 or more is very likely to have a COVID-19 infection, whereas a person with an NLR of less than 5.5 can be excluded from having a COVID-19 infection. Moreover, the NLR value of 5.5 seemed to be a useful tool in differentiating between ICU and non-intensive COVID-19 patients. Using an NLR value of 5.5 to compare between ICU and non-intensive COVID-19 patients gave a very good sensitivity at 86.36% and specificity of 78.9%. Moreover, the yielded negative predictive value was 92.9%. In other words, confirmed COVID-19 patients with an NLR of 5.5 or more, should be observed carefully as they are more prone to become ICU patients, while those with an NLR less than 5.5 will most likely be non-intensive patients. Discussion. Since the beginning of the COVID-19 pandemic, healthcare systems strived to develop diagnostic tools, as well as identifying prognostic markers as it is currently without a definitive treatment. Although it was initially thought to be a respiratory infection, increasing evidence have demonstrated its systematic manifestation indicating that it is more than just a respiratory condition. Provided its systematic effect, studies have started to identify prominent hematological changes that served as an independent indicator for the disease severity. Of these markers, NLR was found to be significantly higher in cases of COVID-19 infection, and an indicator of severe forms of the disease. The aim of this pilot case-control study in Saudi Arabia was to compare the laboratory findings in patients with COVID-19 to healthy controls, as well as to assess the value of NLR in COVID-19 infection. In this study, patients had significantly lower hemoglobin levels and platelet count, which are in line with the results shown by Sun et al. 13 Interestingly, the patients' cohort were significantly younger compared to the control group. The median age of patients in this study was 35 years old, which was similar to the national cohort previously described by Alsofayan et al 14 as well as Al-Omari et al. 15 However, the ICU cohort was significantly older than the non-intensive patients, confirming the works of Yi et al 16 and Rosenthal et al 17 that age was an independent risk factor for COVID-19 infection. In our study, the NLR values of patients were significantly higher in patients compared to control 20, 22, 23 Study limitations. Although every effort was carried out to execute this study in a proper manner, this study is not without limitation. In order to validate the predictive value of NLR, ideally it should be tested longitudinally in a prospective study. In other words, the NLR should be determined upon admission and patients are to be followed up to assess how accurate the NLR value in determining the disease outcome. The control group )n=250( in this study were patients who were admitted for elective surgical procedures. Although they tested negative for COVID-19 infection and were fit for the scheduled procedure, other infections and comorbidities were not ruled out. Ideally, the control group should be consisted of healthy volunteers, in a number that is close to tested cohort, and should not have any infections nor comorbidities that may influence the NLR. In conclusion, NLR is an important tool in determining the status of the COVID-19 infection. Although its sole use in COVID-19 diagnosis may not be very accurate, its use in conjunction with a proper history-taking and physical examination should be very useful in ruling out the infection. Furthermore, the findings of this study further confirm that NLR is an independent prognostic factor of a severe infection, and those patients with high NLR should be closely monitored and managed. 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The authors express their thanks and gratitude to Ms. Fong H. Yuen for her support and assistance in the data collection process. The authors would also like to thank Scribendi (www.scribendi.com) for English language editing.