European Journal of Cardiovascular Medicine

Necrotizing soft tissue infections (NSTIs) are rapidly progressive and potentially fatal conditions characterized by widespread fascial necrosis, systemic toxicity, and high morbidity and mortality rates. Early recognition and aggressive intervention remain the cornerstones of successful management. Despite advances in diagnostic and therapeutic strategies, delayed diagnosis continues to significantly impact patient outcomes [1].

Clinically, NSTIs often present with non-specific signs such as pain, swelling, erythema, and systemic symptoms, which may overlap with less severe soft tissue infections [2]. This diagnostic ambiguity underscores the need for reliable diagnostic modalities that can rapidly differentiate NSTI from other infectious processes.

Radiological imaging plays a pivotal role in early detection. Modalities such as computed tomography (CT) and magnetic resonance imaging (MRI) have demonstrated varying degrees of sensitivity and specificity in the diagnosis of NSTIs. A systematic review by Kwee and Kwee reported pooled sensitivities of up to 94% for MRI and 80% for CT in detecting necrotizing infections [3]. While MRI offers superior soft tissue contrast, its availability and acquisition time may limit its practicality in emergent settings [4].
Microbiological testing, particularly culture and sensitivity of tissue or fluid samples, remains a definitive component of diagnosis and guides targeted antimicrobial therapy. However, the diagnostic yield and timing of microbiological results can be variable. Singh et al. highlighted the polymicrobial nature of NSTIs, often involving anaerobes and gram-negative organisms, which may complicate timely organism identification [5]. Naamany et al. also demonstrated significant heterogeneity in the microbial profiles of monomicrobial versus polymicrobial NSTIs, affecting both presentation and prognosis [3,6].

In this context, the present study aims to compare radiological and microbiological diagnostic strategies in NSTIs, focusing on their sensitivity, specificity, time to diagnosis, inter-modality agreement, and predictive value for clinical outcomes. By identifying the relative strengths and limitations of each approach, this work seeks to inform a more integrated and efficient diagnostic algorithm for managing this critical condition.

Study Objective

The objective of this retrospective study was to compare the diagnostic performance of radiological imaging and microbiological testing in patients with suspected necrotizing soft tissue infections (NSTIs). Specifically, the study aimed to:

1. Assess the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of radiological and microbiological modalities against confirmed NSTI status.
2. Compare the time to diagnosis for radiology and microbiology.
3. Evaluate the diagnostic agreement between the two modalities using Cohen’s kappa statistic.
4. Determine the association between diagnostic modality and clinical outcomes, including mortality and limb amputation.
5. Identify independent predictors of mortality through multivariate logistic regression analysis

This retrospective observational study was conducted at Patna Medical College and Hospital, a tertiary care teaching hospital in India. The study included patients admitted between January 2024 and May 2025 with clinical suspicion of necrotizing soft tissue infections (NSTIs). The study was approved by the institutional ethics committee, and data were anonymized prior to analysis.

A total of 100 consecutive patients with suspected NSTIs were included. Inclusion criteria were adult patients (≥18 years) presenting with soft tissue infections requiring evaluation via radiological imaging and microbiological sampling. Patients with incomplete records or lacking confirmatory data were excluded.

All patients underwent radiological evaluation (CT or MRI, depending on clinical urgency and availability) and microbiological testing (culture and Gram stain from tissue or fluid samples). Radiological and microbiological results were categorized as positive or negative based on radiologist interpretation and culture results, respectively. Confirmed NSTI cases were defined by surgical findings, clinical progression, and intraoperative documentation.

Data collected included age, sex, time to diagnosis (from hospital admission to radiological or microbiological confirmation), radiology and microbiology results, final NSTI status, mortality, and limb amputation. Time to diagnosis was recorded in hours. All data were extracted from electronic medical records and verified by two independent reviewers.

Diagnostic accuracy was evaluated by calculating sensitivity, specificity, PPV, and NPV for both radiology and microbiology. An independent t-test was used to compare time to diagnosis between modalities. Cohen’s kappa was used to assess inter-modality agreement. Associations between diagnostic modality and clinical outcomes (mortality and amputation) were tested using chi-square analysis. A multivariate logistic regression model was used to identify independent predictors of in-hospital mortality. A p-value of <0.05 was considered statistically significant. All analyses were performed using SPSS (version 29).

Study Population

A total of 100 patients were included in this retrospective study conducted at Patna Medical College and Hospital from January 2024 to May 2025. The mean age was 52.5 ± 13.3 years, with a slight female predominance (48.0% / 52.0%). Age distribution showed that the majority of patients were aged between 31 and 60 years, accounting for over 70% of the cohort (Table 1). Approximately 63.0% of patients were confirmed to have NSTIs. Radiological investigations were positive in 59.0% of cases, while microbiological confirmation was noted in 38.0%. Mortality among NSTI patients was 41.3%, compared to 2.7% in non-NSTI cases. Amputation was also more prevalent among NSTI patients (47.6%) compared to non-NSTI patients (0.0%).

Table 1. Baseline Characteristics of Study Participants

Diagnostic Performance of Modalities

The diagnostic accuracy of radiological and microbiological modalities was evaluated against confirmed NSTI cases. Radiological imaging demonstrated higher sensitivity (79.4%) but lower specificity (75.7%) compared to microbiological testing, which had a sensitivity of 57.1% and a markedly higher specificity of 94.6%. The positive predictive value (PPV) was high for both modalities, being 84.7% for radiology and 94.7% for microbiology. However, the negative predictive value (NPV) was limited for both, especially for microbiology (56.5%). (Table 2, Figure 1).

A logistic regression model was used to identify predictors of in-hospital mortality. The presence of confirmed NSTI was found to be a statistically significant predictor (OR = 3.40, p = 0.003), indicating a substantially increased risk of mortality. Neither radiological nor microbiological positivity independently predicted mortality. Age showed a non-significant trend toward decreased risk (p = 0.089), while sex was not a significant factor (Table 3).

Table 2. Diagnostic Accuracy Metrics for Radiology and Microbiology

Table 3. Logistic Regression for Predictors of In-Hospital Mortality

Figure 1. Diagnostic Accuracy Metrics for Radiology and Microbiology

Bar chart comparing the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of radiological versus microbiological diagnostic modalities for necrotizing soft tissue infections. Radiology demonstrated higher sensitivity, while microbiology exhibited superior specificity and PPV.

Time to Diagnosis

The mean time to diagnosis was significantly shorter for radiological evaluation compared to microbiological confirmation. Radiology achieved a diagnosis in 5.8 ± 3.8 hours, while microbiological results were available only after 18.8 ± 8.2 hours. The difference was statistically significant (p < 0.001) based on an independent t-test. These findings highlight the value of radiological assessment for prompt identification of necrotizing soft tissue infections, which is critical for early intervention (Figure 2).

Figure 2. Time to Diagnosis by Diagnostic Modality

Box plot comparing the time to diagnosis between radiological and microbiological modalities. Radiological assessment yielded significantly faster diagnostic results (mean ≈ 4.5 hours) compared to microbiology (mean ≈ 28.5 hours), highlighting its value in the early identification of necrotizing soft tissue infections. The difference was statistically significant (p < 0.001).

Agreement Between Modalities

The agreement between radiological and microbiological diagnostic modalities was assessed using Cohen’s kappa statistic. Among the 100 patients, there was only fair agreement between the two tests (κ = 0.25). The cross-tabulation revealed a substantial number of discordant results, indicating that radiology and microbiology often identified different cases as positive. This suggests that the two modalities may complement rather than substitute each other in the diagnostic pathway for necrotizing soft tissue infections (Table 4).

Table 4. Cross-Tabulation of Radiology and Microbiology Results

Clinical Outcomes

Mortality and limb amputation rates were analyzed in relation to the results of radiological and microbiological diagnostics. There was no statistically significant association between radiological findings and mortality (p = 0.504) or amputation (p = 0.092). Similarly, microbiological positivity did not significantly correlate with mortality (p = 0.006) or amputation (p = 0.345). These findings suggest that while these diagnostic tools are critical for early identification, they may not independently predict clinical outcomes such as survival or limb preservation. (Table 5).

Table 5. Clinical Outcomes by Diagnostic Modality Results

Summary of Key Findings

This retrospective study compared the diagnostic value of radiological and microbiological modalities in 100 patients with suspected necrotizing soft tissue infections (NSTIs). Radiological imaging demonstrated superior sensitivity (79.4%) and a faster mean time to diagnosis (4.5 hours), whereas microbiological testing had higher specificity (94.6%) and PPV (94.7%), though at the cost of a significantly longer diagnostic time (mean 28.5 hours). Agreement between the modalities was only fair (Cohen’s κ = 0.25), underscoring their complementary roles. Logistic regression confirmed that the presence of NSTI was a strong and independent predictor of mortality (p = 0.003), while neither radiology nor microbiology alone significantly influenced mortality risk. No statistically significant associations were found between diagnostic results and limb amputation or death. These findings highlight the critical role of combining rapid imaging with confirmatory microbiology in ensuring timely diagnosis and management of NSTIs.

This study evaluated the comparative effectiveness of radiological and microbiological modalities in the diagnosis of necrotizing soft tissue infections (NSTIs). Radiological imaging demonstrated a higher sensitivity (79.4%) compared to microbiological testing (57.1%), while microbiology provided superior specificity (94.6% vs. 75.7%) and PPV (94.7% vs. 84.7%). These findings align with Spinnato et al. [7] and Hayeri et al. [10], who emphasized the early diagnostic value of imaging, particularly CT and MRI, in differentiating NSTIs from other soft-tissue infections. Microbiology, although definitive, often lags in timeliness and may miss early cases, consistent with limitations reported by Wilson and Winn [12] and Shiroff et al. [13].

The mean time to diagnosis via radiology was 5.8 ± 3.8 hours, significantly shorter than microbiological confirmation, which averaged 18.8 ± 8.2 hours (p < 0.001). This delay is critical in the clinical context, where early intervention drastically alters outcomes [14, 15]. Hua et al. [14] reinforced the role of rapid imaging in expediting surgical decision-making, while Nawijn et al. [15] highlighted delays in microbiology as a persistent barrier to optimal care. Our findings substantiate the time-sensitive advantage of radiology in acute NSTI evaluation.

Cohen’s kappa statistic between radiology and microbiology was 0.25, indicating only fair agreement. This suggests that the two modalities often identify different subsets of NSTI cases, underscoring their complementary diagnostic value. Similar observations were noted by Wu et al. [9] in their fluid analysis pilot, where imaging and laboratory data diverged but jointly improved diagnostic yield.

Microbiological positivity was significantly associated with mortality in univariate analysis (p = 0.006), while radiology positivity vs. mortality had a p-value of 0.504. Neither modality, however, was predictive of amputation (p = 0.092 for radiology, p = 0.345 for microbiology). These results suggest that although diagnostics aid in early detection, outcomes may be more strongly influenced by disease severity and timeliness of surgical intervention rather than test modality alone, consistent with findings by Madsen et al. [16] and Hussein & Anaya [17].

Multivariate logistic regression confirmed that confirmed NSTI diagnosis was an independent predictor of mortality (β = 3.40, p = 0.003). Radiology and microbiology positivity were not independently associated with mortality (p = 0.982 and 0.382, respectively), nor were age (p = 0.089) or sex (p = 0.879). These findings reinforce that the presence of NSTI itself drives clinical outcomes, echoing prior studies by Stevens et al. [11] and Tessier et al. [8], which underline the need for aggressive early management in confirmed NSTI regardless of diagnostic modality.

This study demonstrates that radiological imaging offers a more rapid and sensitive diagnostic approach for necrotizing soft tissue infections compared to microbiological testing, which, despite its specificity, is limited by delayed results. The fair agreement between modalities suggests that both tools contribute uniquely to clinical diagnosis. The presence of confirmed NSTI was the strongest predictor of mortality, emphasizing the need for high clinical vigilance and early intervention. These findings support the integration of prompt radiological evaluation into the standard diagnostic workflow for NSTI.

LIMITATIONS

This study has several limitations. First, it is retrospective in nature and confined to a single tertiary care center, which may limit generalizability. Second, the sample size of 100 patients, while sufficient for exploratory analysis, may not capture more nuanced associations or subgroup variations. Third, diagnostic accuracy was assessed using binary positive/negative results, potentially oversimplifying the spectrum of radiological and microbiological findings. Finally, outcomes such as mortality and amputation may be influenced by factors not captured in this dataset, including time to surgical debridement, comorbidities, and antibiotic protocols.

1. Kwee, R. M., & Kwee, T. C. (2022). Diagnostic performance of MRI and CT in diagnosing necrotizing soft tissue infection: a systematic review. Skeletal Radiology, 1-10.
2. Singh, G., Ray, P., Sinha, S. K., Adhikary, S., & Khanna, S. K. (1996). Bacteriology of necrotizing infections of soft tissues. Australian and New Zealand journal of surgery, 66(11), 747-750.
3. Naamany, E., Shiber, S., Duskin-Bitan, H., Yahav, D., Bishara, J., Sagy, I., ... & Drescher, M. (2021). Polymicrobial and monomicrobial necrotizing soft tissue infections: comparison of clinical, laboratory, radiological, and pathological hallmarks and prognosis. A retrospective analysis. Trauma Surgery & Acute Care Open, 6(1).
4. Goldstein, E. J., Anaya, D. A., & Dellinger, E. P. (2007). Necrotizing soft-tissue infection: diagnosis and management. Clinical infectious diseases, 44(5), 705-710.
5. Bonne, S., & Kadri, S. S. (2017). Evaluation and management of necrotizing soft tissue infections. Infectious disease clinics of North America, 31(3), 497.
6. Leichtle, S. W., Tung, L., Khan, M., Inaba, K., & Demetriades, D. (2016). The role of radiologic evaluation in necrotizing soft tissue infections. Journal of Trauma and Acute Care Surgery, 81(5), 921-924.
7. Spinnato, P., Patel, D. B., Di Carlo, M., Bartoloni, A., Cevolani, L., Matcuk, G. R., & Crombé, A. (2022). Imaging of musculoskeletal soft-tissue infections in clinical practice: a comprehensive updated review. Microorganisms, 10(12), 2329.
8. Tessier, J. M., Sanders, J., Sartelli, M., Ulrych, J., De Simone, B., Grabowski, J., ... & Duane, T. M. (2020). Necrotizing soft tissue infections: a focused review of pathophysiology, diagnosis, operative management, antimicrobial therapy, and pediatrics. Surgical infections, 21(2), 81-93.
9. Wu, K. H., Wu, P. H., Chang, C. Y., Kuo, Y. T., Hsiao, K. Y., Hsiao, C. T., ... & Chang, C. P. (2022). Differentiating necrotizing soft tissue infections from cellulitis by soft tissue infectious fluid analysis: a pilot study. World Journal of Emergency Surgery, 17(1), 1.
10. Hayeri, M. R., Ziai, P., Shehata, M. L., Teytelboym, O. M., & Huang, B. K. (2016). Soft-tissue infections and their imaging mimics: from cellulitis to necrotizing fasciitis. Radiographics, 36(6), 1888-1910.
11. Stevens, D. L., Bryant, A. E., & Goldstein, E. J. (2021). Necrotizing soft tissue infections. Infectious Disease Clinics, 35(1), 135-155.
12. Wilson, M. L., & Winn, W. (2008). Laboratory diagnosis of bone, joint, soft-tissue, and skin infections. Clinical infectious diseases, 46(3), 453-457.
13. Shiroff, A. M., Herlitz, G. N., & Gracias, V. H. (2014). Necrotizing soft tissue infections. Journal of intensive care medicine, 29(3), 138-144.
14. Hua, C., Urbina, T., Bosc, R., Parks, T., Sriskandan, S., de Prost, N., & Chosidow, O. (2023). Necrotising soft-tissue infections. The Lancet Infectious Diseases, 23(3), e81-e94.
15. Nawijn, F., Hietbrink, F., Peitzman, A. B., & Leenen, L. P. (2021). Necrotizing soft tissue infections, the challenge remains. Frontiers in surgery, 8, 721214.
16. Madsen, M. B., Arnell, P., & Hyldegaard, O. (2020). Necrotizing soft-tissue infections: clinical features and diagnostic aspects. Necrotizing Soft Tissue Infections: Clinical and Pathogenic Aspects, 39-52.
17. Hussein, Q. A., & Anaya, D. A. (2013). Necrotizing soft tissue infections. Critical care clinics, 29(4), 795-806.