Letter to the Editor: “Systemic Inflammation Response Index and Systemic Immune Inflammation Index Are Associated with Clinical Outcomes in Patients with Acute Pancreatitis”

To the editor,

The paper titled “Systemic Inflammation Response Index and Systemic Immune Inflammation Index Are Associated with Clinical Outcomes in Patients with Acute Pancreatitis” documented that these calculated hematological indexes can potentially predict the clinical outcomes of patients with acute pancreatitis (AP) [1]. The Systemic Inflammation Response Index (SIRI) was calculated as SIRI = (N × M)/L, while SII was defined as SII = (P × N)/L, where peripheral blood lymphocyte (L), monocyte (M), neutrophil (N), and platelet (P) counts were used in cells/liter [1]. According to this paper these easily available, low-cost hematologic parameters can be useful in predicting the clinical course of severe inflammatory diseases including AP. This is especially relevant according to a 2019 publication which showed that the rate of hospitalization for AP increased from 65.38 to 81.88 per 100,000 US adults per year from 2001 to 2014 [2]. The organ specific or localized inflammatory response triggered in patients with AP or severe acute pancreatitis (SAP) has also long been associated with a larger, systemic response which may lead to further clinical complications including mortality [3]. The list of serious complications often includes acute kidney injury (AKI), which was found to occur in up to 69% of patients with SAP [4]. Previously, other studies reported on the use of Systemic Immune Inflammation Index (SII) as a reliable indicator of disease severity and a potential predictive marker for AKI in patients with SAP [5, 6]. In the publication we are commenting on, the authors expanded on those previous findings by employing SII alongside the systemic inflammation response index (SIRI), reporting the latter’s first use as an additional and clinically useful predictive biomarker for the development of AKI in AP patients [1]. The clinical data of 332 patients analyzed in this work demonstrated a clear predictive association between these elevated markers and disease severity of AP, as well as the ability of these marker values to independently differentiate between SAP and AKI. Because SII and SIRI are both calculated from laboratory results of simple blood tests, employing them in a clinical setting is convenient and practical. With easy access to these predictive results, clinicians can better plot the course of treatment and better anticipate complications in their patients. Furthermore, early quantification of these inflammatory markers allows for more diagnostic insight and could improve both the morbidity and mortality of AP. Consequently, these tests could save valuable time and money in the hospital setting.

While the potential ramifications of the data are promising, the authors caution against generalizing the results due to the study’s small sample size (n = 332) and its retrospective nature. They also point out that the complete blood count (CBC) data in this study were limited to two (2) time points at 24 and 48 h, which may not be convincing enough due to the continually changing flow of certain inflammatory responses, especially those involved in pancreatitis [7]. Furthermore, the fact that the study comes from a single healthcare institution should be considered a limitation.

Additionally, the role of other sources of systemic inflammatory responses and their effects on SII and SIRI values are not discussed. This is especially relevant due to SIRI’s use in predicting the severity of more chronic conditions, such as rheumatoid arthritis [8]. As a result, patients with coinciding chronic and acute inflammatory conditions may not be ideal candidates for screening of this nature unless the screening is expanded with additional, case-specific parameters. It may be worthwhile to include other hematological parameters more actively such as the patient’s neutrophil-to-lymphocyte ratio (NLR), since these blood cell counts will already be on hand and NLR values alone have been used to evaluate patients with both pancreatitis and chronic kidney disease in the past [9, 10]. The incorporation of other diagnostically relevant values may even allow for the screening to be adapted to other chronic conditions, such as those mentioned above, in addition to more acute or systemic inflammatory conditions like pneumonia, peritonitis, clostridium difficile infection or even sepsis, due to the characteristic and specific inflammation in their pathogenesis [10]. Further studies expanding and diversifying the sample to be more representative of the overall population will determine the robustness of the prediction model at a true clinical scale.

Overall, the authors presented a novel, yet simple and economically viable screening method for predicting the disease courses of both AP and SAP patients. The promise of a practically useful and simple way of triaging and treating these patients by severity and risk of complications including death during the first days of hospital care calls for further research in this area. This is especially true due to its potential to significantly improve patient outcomes and hospital resource management.

Disclosure statement

The authors report no conflict of interest.