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| ORIGINAL ARTICLE |
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| Year : 2022 | Volume
: 28
| Issue : 2 | Page : 133-137 |
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LRINEC (Laboratory Risk Indicator for Necrotizing Fasciitis) scoring system as a predictor for early diagnosis of necrotizing fasciitis in soft-tissue infections
C Rajeev1, A Mohamad Safwan2, K P C Muhammed Irfan3, KN Vijayan2, Liju Varghese4
1 Department of General Surgery, General Hospital Thalassery, Palissery, Thalassery, Kerala, India
2 Department of General Surgery, KIMSHEALTH Hospital, Thiruvananthapuram, Kerala, India
3 Department of General Surgery, Government Medical College Hospital Manjeri, Vellarangal, Manjeri, Kerala, India
4 Department of General Surgery, Kaduvayil Thangal Charitable Trust Hospital, Chathampara, Thottakkadu, Kallambalam, Thiruvananthapuram, Kerala, India
| Date of Submission | 22-Nov-2022 |
| Date of Decision | 28-Nov-2022 |
| Date of Acceptance | 02-Dec-2022 |
| Date of Web Publication | 30-Jan-2023 |
Correspondence Address:
Dr. C Rajeev
Department of General Surgery, KIMSHEALTH Hospital, Thiruvananthapuram - 695 029, Kerala
India
 Source of Support: None, Conflict of Interest: None
DOI: 10.4103/ksj.ksj_45_22
Introduction: Necrotizing soft-tissue infections are often fatal, characterized by extensive necrosis of the fascia and subcutaneous tissues. To aid the early diagnosis of necrotizing fasciitis (NF), there is a Laboratory Risk Indicator for Necrotizing Fasciitis (LRINEC) scoring system for the early diagnosis of NF. Our study was undertaken to evaluate LRINEC score, based on routine laboratory investigations that are readily available, that could help distinguish NF from other soft-tissue infections. Materials and Methods: The study was conducted on all inpatients, admitted with features of soft-tissue infections suspected to have NF and later underwent wound debridement or amputation in a tertiary care hospital. LRINEC score more than or equal to 6 was considered as case and the score <6 considered as control. Both were treated with intravenous (IV) antibiotics, IV fluids and surgical intervention based on their clinical findings and outcome. The confirmatory diagnosis for NF was done through culture of tissue and other body fluids. Results: The cutoff value of LRINEC for predicting NF was 6 with sensitivity of 85.7% and specificity of 70.7%. The negative predictive value of LRINEC-OC was 87.9% and positive predictive value (PPV) 66.7%. The accuracy was 76.8%. Conclusion: LRINEC scoring system has a better PPV in identifying the onset of NF and risk strategizing of the patients with severe soft-tissue infections. We recommend LRINEC score to be used as a predictor in the diagnosis of NF. Multi-disciplinary team may guide immediate operative and supportive management, thereby improving the clinical outcome of the patient.
Keywords: Immunocompromised, necrotizing fasciitis, soft-tissue infection
How to cite this article:
Rajeev C, Safwan A M, Muhammed Irfan K P, Vijayan K N, Varghese L. LRINEC (Laboratory Risk Indicator for Necrotizing Fasciitis) scoring system as a predictor for early diagnosis of necrotizing fasciitis in soft-tissue infections. Kerala Surg J 2022;28:133-7 |
How to cite this URL:
Rajeev C, Safwan A M, Muhammed Irfan K P, Vijayan K N, Varghese L. LRINEC (Laboratory Risk Indicator for Necrotizing Fasciitis) scoring system as a predictor for early diagnosis of necrotizing fasciitis in soft-tissue infections. Kerala Surg J [serial online] 2022 [cited 2023 Mar 24];28:133-7. Available from: http://www.keralasurgj.com/text.asp?2022/28/2/133/368602 |
| Introduction | |  |
Necrotizing fasciitis (NF) is a rare but life-threatening soft-tissue infection characterized by rapidly progressive necrosis of subcutaneous tissues and deep fascia planes, with resulting skin gangrene and severe systemic infection.[1] It is a rapidly progressive inflammatory condition of the fascia with secondary necrosis of the subcutaneous tissues. NF moves along the fascial plane, as blood supply to the fascia is weaker than that of muscle or skin and thus the fascia is more vulnerable to infectious processes.[2]
The incidence of NF has been reported to be 0.40 cases per 1 lakh population.[3] Although NF is rare, certain conditions including immunocompromised states such as diabetes mellitus, chronic kidney disease, malignancies, chronic liver diseases, and steroid users predispose to develop NF and also those with intravenous (IV) drug or collagen vascular disease patients. Lack of specific clinical features and characteristics in the initial stages of the disease may be the main reason for the failure of early recognition of NF.[4],[5] The median mortality rate for NF is 32.2% but varies throughout the literature from 8.7% to 76%.[2]
Patients with NF must be promptly and aggressively treated with surgical intervention to reduce morbidity and mortality.[2],[4] The extremities, groin, and abdomen are the sites most frequently affected by the disease. Early diagnosis is missed or delayed in 85%–100% of cases in large published series because of the lack of specific clinical features in the initial stage of the disease.[6]
Due to the lack of clinical findings, laboratory investigations and other imaging techniques play an important role in the early diagnosis of the devastating illness. Here we were discussing about such a scoring system Laboratory Risk Indicator for Necrotizing fasciitis (LRINEC) based on laboratory investigations as a tool that aids in early identification patients with NF and help to decide on early intervention and effective surgical and supportive therapy to modify clinical outcome.
| Materials and Methods | | |
The aim of the study was to validate LRINEC Scoring system as a predictor in the early diagnosis of NF. The primary objective was to validate the significance of LRINEC Score ≥6 as a predictor for diagnosing NF and to intervene early for better care and prevention of developing complications of NF.
It was a prospective, observational study conducted from July 2019 to July 2020 in patients between 18 and 75 years of age, who admitted in a tertiary care hospital with features of cellulites and soft-tissue infections with fever, painful limb swellings, gangrenous changes, tachycardia, edematous extremities with acute onset of symptoms <48 h, and not received IV antibiotics minimum of three doses and later undergone wound debridement or amputation.
Patients who had received antibiotic treatment in the last 48 h or had received a minimum of three doses of antibiotics prior to presentation, patients who had undergone surgical debridement for present episode of soft-tissue infection, and patients with burns or furuncles with no evidence of cellulitis were excluded from the study.
Sample size estimation
Required sample size (n) was calculated using the formula
Then, 
Accordingly, 70 patients were included in this study.
Patients presenting with features of soft-tissue infections inflammation, edema, pain, erythema, ulcer, and fever were categorized as equivocal necrotizing soft-tissue infections. Laboratory examinations were ordered at the time of admission including white blood cell (WBC) count, hemoglobin, creatinine, sodium, glucose, C-reactive protein (CRP), blood culture, and wound culture if wound presented or operation performed. The enrolled patients were divided into two groups, the NF group and the equivocal necrotizing soft-tissue infections, according to the following criteria: The diagnosis of NF was confirmed by the final operative and pathologic findings of NF. The operative findings included presence of necrotic fascia and pus-like fluid. The pathology evidence of NF consisted of necrosis, polymorphonuclear infiltration, vasculitis, and thrombosis in the tissue.
Based on laboratory parameters obtained and the information obtained using a pretested semi-structured pro forma, LRINEC score was calculated to each of the equivocal subjects. LRINEC score more than or equal to 6 was considered as cases and score <6 considered as controls. Both were treated with IV antibiotics, IV fluids, and surgical intervention based on their clinical findings and outcome. The confirmatory diagnosis for NF was done through culture of tissue and other body fluids.
All the data collected through the pro forma were entered into the Microsoft Excel and analyzed using the statistical software SPSS version 16.0 (IBM, Delhi). Different variables were used to rule out the significance of LRINEC scoring system for the early diagnosis of NF in soft-tissue infections. The results on categorical variables were represented using frequencies and percentages. P < 0.05 was considered as statistically significant.
| Results | | |
Management of soft tissue infections is given in the [Flow Chart 1]. Seventy patients were included, age ranging from 18 years to 75 years and with a mean of 61.59 ± 8.71 years. Most of the patients were above 50 years of age. 48 out of 70 were males (68%) and 22 were females (31%). NF is almost two fold more common among males. Most of the patient had edema, inflammatory signs like erythema or glossy appearance. Only 14.6% (10) had necrosis at the time of presentation and 0.85% (6) were detected to have crepitus. 92.8% (65) had inflammation, edema 95.4% (67), and 35.6% (25) of patients had ulcer in the affected part at the time of presentation.
Most of the patients in the study population had diabetes mellitus (84.2%). The other common comorbidities were systemic hypertension, coronary artery disease, and chronic liver disease which comprised 62.3%, 43.5%, and 11.6%, respectively.
LRINEC score was high in 47.8% patients of study population. The LRINEC score of the study population had a sensitivity of 71.4% at 6.5 and specificity of 92.7%. The specificity reached up to 100% considering the score as 8.5.
LRINEC score composed of six variables. Hemoglobin <11 g/dl in 39 patients, only 5 out of 70 patients did not have anemia at the time of presentation. 62.35% of patients had TLC <15,000. 48.5% patients had elevated creatinine level. 48.5% in sample populations had raised sugar values. 42.9% in sample populations had elevated CRP than 150. 42% patients had hyponatremia in the sample population. In the study population, 40.6% patients had histopathological diagnosis as necrotizing infection.
Majority of the study population became symptomatically better, amputation done for 8 patients all of them had score more than 6; 7 deaths occurred that too from high risk group. All patients in low risk group became symptomatically better after conservative line of management.
Among the diabetic patients in high risk group, five of them got improved with resuscitative measures and multiple surgical debridement; 8 patients required amputation of the affected part and 7 patients succumbed to death [Figure 1].
An receiver operating characteristic (ROC) curve based on a cutoff LRINEC score of ≥6 in predicting the presence of NF was plotted to find out a new cut off from the data in predicting the presence of NF. The area under the ROC curve came to be 0.869 with a P < 0.01 which is statistically significant [Figure 2].
The relation between LRINEC score and NF had sensitivity of 85.7%, specificity of 70.7%, positive predictive value (PPV) of 66.7%, negative predictive value (NPV) of 87.9%, the accuracy was 76.8%, and with P < 0.01 which is statistically significant.
The cutoff value of LRINEC for predicting NF was 6.5 with sensitivity of 71.4% and specificity of 92.70%. The cutoff value of LRINEC for predicting NF was 7.5 with sensitivity of 64.30% and specificity of 95.10%. The cutoff value of LRINEC for predicting NF was 8.5 with sensitivity of 60.70% and specificity of 100% [Figure 3].
| Discussion | | |
In the present study, patients were categorized using LRINEC score which is based on a fixed set of investigation parameters. Those having LRINEC score <6 were categorized as low risk and >6 were categorizes high risk. In all, 47.8% of the patients belonged to low risk group, and 52.2% to high-risk group. Furthermore, it is seen that males significantly outnumbered females and the soft-tissue infections were the most common in the 50–60 age group. Hence, it was found that the risk profile increases with advancing age as revealed by the significant P < 0.001.
In our study, edema and inflammation were the most common symptoms similar to the study by Goh et al.[7] Out of 70 diabetic patients, 41.4% had NF and 58.6% didn't have the disease. In our study, diabetes mellitus was the most common associated comorbidity seen among (84%) of patients similar to studies by Wong et al.,[2] Tan et al.,[8] and others were hypertension (63.2%) and coronary artery disease (43%).
The LRINEC score was first proposed by Wong et al.[2] with the purpose of distinguishing NF and other soft-tissue infections using routine biochemical tests. Based on his study, the cutoff value of 6 showed PPV of 92% and 2 showed NPV of 96%.
In the present study, when taking LRINEC score cutoff at “6,” the sensitivity is 85.70%, specificity 70.7%, PPV 66.7%, and NPV 87.9% in the diagnosis of necrotizing infection. It was almost similar to other studies conducted wherein they validated the LRINEC scores with an ROC of 0.925, sensitivity of 76.3%, specificity of 93.1%, and positive and NPVs of 95.5% and 88.1% based on an LRINEC value of ≥6 to distinguish NF from severe cellulitis.[9]
Sirikurnpiboon and Sawangsangwattana. reported a sensitivity of 85.42%, specificity of 75.31%, PPV 67.21%, NPV 89.71% and accuracy 79.07%.[10]
Liao et al.[11] studied 235 patients and found that a LRINEC score ≥6 had a sensitivity of 59.2% (confidence interval [CI] 52.9%–65.6%), specificity of 83.8% (CI 81.9%–85.7%), likelihood ratio of 3.89, and positive predictive ratio of 37.9% (95% CI 32.9%–42.9%), and negative predictive ratio of 92.5% (95% CI 91.0%–94.0%) almost similar to our study. The decrease in sensitivity and specificity may be attributed to difference in sample size.
From our study, we suggest that the LRINEC scoring system could be a reliable predictor for differentiating NF from other types of soft-tissue infection. ROC curve for a score of 6 showed the area under the curve <1 (0.869), which was clinically significant.
A retrospective study by Chao et al.[12] indicated that the LRINEC score may prove accurate when used for NF fasciitis in the risk stratification and the differentiation of cellulitis from NF.
On correlating systemic complications of soft-tissue infections with LRINEC score, it was found that patients of the high-risk group had more sepsis-related complications. In the present study, it was found that almost three fourth of the patients in low-risk group were managed conservatively (90.7%), while most of the patients of the high-risk group required surgical intervention. Most common surgical intervention required in the high-risk group was debridement and/or fasciotomy with a good proportion of them requiring secondary skin grafting or suturing (8 out of 28 patients). Amputation was required in 8 of the patients that too in the high-risk category.
From the data, it can be clearly seen that surgery is the mainstay of treatment in severe soft-tissue infections based on LINREC score, especially NF. In the present study, mortality was most common in the patients of the high-risk group and 7 out of 25 patients died during the course of treatment. The distribution was highly significant with a P < 0.001. This shows that an aggressive treatment plan can be instituted on a timely manner. This finding was similar to those of Yaghoubian et al.[13] in which the rate of mortality remains as high as 24%–34%; posing a challenge for the diagnosis and management. Furthermore, rates of mortality (25%) and amputation (28.6% in patients with LRINEC score ≥6 were higher than those who had LRINEC <6.
The laboratory variables used to calculate LRINEC scoring are found to correlate individually with the diagnosis of NF in a study by Goh et al.[7] It can be concluded that high CRP, raised WBC, low hemoglobin, and high level of serum creatinine are the strong indicators of NF.
The limitations of our study were small sample size populations of the study; only patients with NF involving the limbs were included in our study. Future prospective validation studies are warranted to determine whether the LRINEC score is a useful tool for discriminating NF from severe cellulitis in other parts of the body, and finally, this was a single-hospital study, and the patient characteristics of the study cohort may be different from other institutions. Thus, our findings may not be applicable to other institutions with different patient characteristics, hospital features, and levels of care. In order to further test the validity of the LRINEC score, a multi-center study from different countries and with a larger sample should be conducted in the future.
| Conclusion | | |
LRINEC scoring system has a better PPV in identifying the onset of NF fasciitis and risk strategizing of the patients with severe soft-tissue infections. We recommend Laboratory Risk Indicator for NF (LRINEC) score can be used as a predictor in the diagnosis of NF, especially in secondary care hospitals and may prevent delayed referral to tertiary centers where experienced surgeons and multidisciplinary team may guide immediate operative and supportive management, thereby improving the clinical outcome of the patient.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]
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