Introduction
In recent years, numerous studies have researched some low-cost, valid, reproducible indicators of inflammation and immunity: the platelet-lymphocyte ratio (PLR) and the neutrophil-lymphocyte ratio (NLR). The results suggest that these combined markers are more satisfactory predictors of prognosis than single-cell counts. As a result, a new index, the systemic immune-inflammation index (SII), is recently introduced for various diseases, including CVD, cancers, and its spread and systemic infective conditions.
How Is the SII Calculated?
SII is calculated by multiplying neutrophil with platelet and dividing it by lymphocyte values.
What Are the Advantages of Using SII?
Routine blood tests for a complete blood count easily obtain SII. It is the most commonly conducted test in clinical practice. This marker has shown higher predictive importance for prognosis in the cancer domain than other inflammatory factors. Interestingly, recent studies suggest that SII can be associated with prognosis and mortality in cases of CVD (cardiovascular disease).
SII is investigated as a marker to anticipate cancer survival in various tumors. This non-invasive prognostic biomarker is inexpensive, reliable, robust, reproducible, and convenient. In addition, it is a better indicator to estimate the instability of the inflammatory response than other markers.
What Is the Role of SII in the Prediction of CVD Prognosis?
Various studies found a significantly high risk of CVD in individuals with high SII levels. Moreover, this risk is observed in nearly every type of CVD. At the onset of various CVD, SII values also significantly increased. According to these findings, SII may indicate people's high risk of CVD and contribute to early diagnosis. Considerable proof suggests that chronic inflammation plays a major role in the pathogenesis of CVD. The SII has unique edges over other biological indicators. The research found that SII had a more promising predictive ability regarding coronary artery disease occurrence than other standard markers.
What Is the Role of SII in the Prediction of Survival in Cancer?
Numerous kinds of research have documented the link between inflammation and cancer and discovered that cancer-related inflammation is a vital component of the tumor microenvironment. Inflammatory cells, such as neutrophils, lymphocytes, and platelets, have an important role in cancer development. In addition, these cells can contribute to tumor cell aggression and distant metastasis. SII is a noninvasive biomarker on three peripheral blood parameters: neutrophil, platelet, and lymphocyte count. Thus, SII can comprehensively reflect the ratio of host immune and inflammatory status, and it is also a more objective marker with better predictive dependability for prognosis. The researchers also tested the hypothesis that high SII scores indicated poor outcomes in cancer patients and found that it accurately predicted one-year survival and tumor differentiation.
The SII index is a significant and cost-effective biological marker for monitoring survival. It has optical prognostic power in various malignancies, including:
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Hepatocellular carcinoma.
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Bladder cancer.
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Lung cancer.
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Pancreatic cancer.
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Gastric cancer.
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Invasive vulvar cancer.
What Is the Role of SII in Predicting the Survival of Older Adults With Hip Fractures?
Hip fracture is a common injury among older adults and has evolved as a global public health problem with high mortality and disability rates. High SII is newly identified as a satisfactory risk predictor for determining osteoporotic fracture risk in postmenopausal osteoporosis women.
Some studies speculate that elevated SII levels due to rising platelet and neutrophil counts and, or low lymphocyte counts can predict poor prognosis in case of hip fracture in older adults.
Researchers observed that dead patients had a remarkably higher SII value than survivors. Moreover, multivariable analysis confirmed that SII is significantly associated with one-year mortality and total mortality.
What Is the Role of SII in Predicting Miscarriages?
High SII values in early pregnancy can be used as an additional marker for predicting possible miscarriage in pregnant women with threatened abortion.
What Is the Role of SII in Predicting Adverse Outcomes in a Pregnant Woman With Coronavirus Disease?
Some studies suggest that SII, combined with other clinical findings and similar markers, may predict poor perinatal outcomes.
What Is the Role of SII in Predicting Sepsis and Systemic Inflammatory Response Syndrome in Odontogenic Infections?
Acute odontogenic infections are the leading reason for emergency visits and hospitalizations in the maxillofacial department and may cause systemic inflammatory complications. However, few studies hypothesized that greater values suggest a higher risk of sepsis and systemic inflammatory response syndrome.
What Is the Role of SII in Predicting Outcomes of Severe COVID-19?
Various retrospective research findings indicate that the blood routine analysis parameters and hemogram-derived ratios differed between severe and non-severe COVID-19 patients. SII has an optimal sensitivity of 81.25 % in predicting the occurrence of severe patients with COVID-19, enhancing reasonable distribution of medical resources to decrease severe patient mortality for clinicians.
Conclusion
SII is a novel marker calculated easily from a complete blood count examination. An innovative index SII has shown an accuracy in various conditions describing imbalance of immunity and inflammation. It is proposed as a tool for predicting prognosis and outcome by various studies data in patients with sepsis, infections, cancers, and CVD. Consequently, increasing evidence indicates a close relationship between patients' inflammation status and infection development and progression of the condition. Therefore, determining patients' inflammation rates becomes crucial in establishing an adequate risk stratification. In this consideration, inflammatory markers can be beneficial for predicting the risk of developing conditions. In addition, The SII is an independent prognostic marker in various systemic conditions, allowing more precise survival estimates than other markers.
