A Report on the Validation of the Laboratory Risk Indicator for Necrotizing Fasciitis (LRINEC) Score and the Establishment of a Novel Score (J-LRINEC) in Japanese Patients

Academic Background

Necrotizing fasciitis (NF) and cellulitis are two common skin infectious diseases. Although they share some similarities in clinical manifestations, their severity and treatment approaches differ significantly. Necrotizing fasciitis is a rapidly progressing and highly fatal infection, while cellulitis is relatively milder. Therefore, accurately distinguishing between these two conditions is crucial for clinical treatment.

The Laboratory Risk Indicator for Necrotizing Fasciitis (LRINEC) score is a widely used tool for differentiating these two diseases. However, previous studies have shown that the sensitivity and specificity of the LRINEC score may vary across different countries and regions, particularly among Japanese patients, where its applicability has not been thoroughly validated. Thus, this study aims to validate the LRINEC score in Japanese patients and develop a novel scoring system (J-LRINEC) more suitable for this population.

Source of the Paper

The paper was authored by Yuta Norimatsu, Takemichi Fukasawa, Yuki Ohno, and others from institutions including JR Tokyo General Hospital, the University of Tokyo Graduate School of Medicine, and the International University of Health and Welfare Narita Hospital. It was published in 2025 in the Journal of Dermatology under the title Validation of Laboratory Risk Indicator for Necrotizing Fasciitis (LRINEC) Score and Establishment of Novel Score in Japanese Patients with Necrotizing Fasciitis (J-LRINEC Score).

Research Process

Study Subjects and Data Processing

This study retrospectively analyzed data from 265 patients hospitalized at JR Tokyo General Hospital and the University of Tokyo Hospital between April 2005 and March 2018, including 56 patients with necrotizing fasciitis and 209 with cellulitis. All diagnoses were based on clinical, imaging, and laboratory findings. The data were randomly divided into a training set (n=199) and a validation set (n=66). Patients with missing data or those with osteomyelitis or pressure ulcer infections were excluded.

Data Analysis

Researchers analyzed non-normally distributed variables using the Mann-Whitney U test and categorical data using Fisher’s exact test or the chi-squared test. To evaluate the effectiveness of the LRINEC score, logistic regression analysis was used to calculate its C-statistic. Additionally, researchers developed a new scoring equation, called the Laboratory Risk Indicator for Necrotizing Fasciitis for Japanese Patients (J-LRINEC) score, using logistic regression analysis and the forward selection method.

Development of the Novel J-LRINEC Score

The formula for the J-LRINEC score is as follows:

[ J-LRINEC\ score = \frac{1}{1 + \exp(-s)} ]

Where,

[ s = -2.19466839641172 - 0.0326642793846153 \times \text{Age} - 0.111283611908592 \times \text{Body Mass Index} + 0.102666886155143 \times \text{CRP Level} + 0.446802301715261 \times \text{Body Temperature} - 3.64811896715886 \times \text{Albumin Level} ]

Main Findings

Patient Characteristics

The study found that patients with necrotizing fasciitis were generally older, had a lower body mass index, and were more likely to be immunosuppressed. Additionally, necrotizing fasciitis was more likely to occur in non-lower extremity sites, and patients exhibited worse vital signs.

Blood Test Results

Patients with necrotizing fasciitis had significantly higher white blood cell counts, blood glucose, hemoglobin A1c, and CRP levels compared to those with cellulitis, while their hemoglobin, sodium, and albumin levels were significantly lower. Patients with necrotizing fasciitis were also more likely to experience renal dysfunction.

Comparison Between the LRINEC Score and the J-LRINEC Score

In the validation set, the LRINEC score had a C-statistic of 0.914, specificity of 96%, but a sensitivity of only 68.9%. In contrast, the J-LRINEC score had a C-statistic of 0.9683, sensitivity of 91.4%, and specificity of 84.8%. This indicates that the J-LRINEC score is more accurate in differentiating necrotizing fasciitis from cellulitis.

Conclusions and Significance

This study validated the effectiveness of the LRINEC score in Japanese patients but highlighted its low sensitivity. As a result, the researchers developed the J-LRINEC score, which demonstrated higher sensitivity and specificity in Japanese patients. The findings suggest that the J-LRINEC score can serve as a complementary tool to the LRINEC score for more accurate differentiation between necrotizing fasciitis and cellulitis, particularly in Japanese patients.

Research Highlights

1. Validation of the LRINEC Score: This study is the first to validate the effectiveness of the LRINEC score in Japanese patients, filling a gap in this field.
2. Development of the J-LRINEC Score: The study developed a novel scoring system, J-LRINEC, which outperformed the LRINEC score in sensitivity and specificity for Japanese patients.
3. Potential Clinical Value: The application of the J-LRINEC score could improve early diagnosis rates of necrotizing fasciitis, thereby enhancing patient outcomes.

Additional Valuable Information

The study also compared other commonly used scoring tools, such as the SIARI score and the NEJM algorithm, finding that none performed as well as the J-LRINEC score in differentiating necrotizing fasciitis from cellulitis. Additionally, the researchers noted that although imaging scoring systems might be useful for diagnosis, magnetic resonance imaging (MRI) is rarely used in routine dermatology practice in Japan, further emphasizing the practical value of the J-LRINEC score.

This study not only validated the applicability of existing tools in Japanese patients but also developed a novel scoring system tailored to this population, holding significant clinical and scientific importance.