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Frozen sections are unreliable for the diagnosis of necrotizing soft tissue infections
Isaac H Solomon1, Rene Borscheid2, Alvaro C Laga1
1Department of Pathology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA.
Abstract:
Necrotizing soft tissue infections are rare but are associated with high rates of morbidity and mortality. The use of bedside or intraoperative frozen sections has been reported to be associated with faster diagnosis and better outcomes; however, to date no large studies have been published to determine the sensitivity and specificity of frozen sections in this setting. Twenty years of cases suspicious for necrotizing soft tissue infection at a large academic referral center were reviewed, blinded to the final clinical diagnosis (gold standard). Cases were assessed for the number of neutrophils, extent of necrosis, presence of thrombi, bacteria, karyorrhexis, and fibrin, and concordance with permanent sections. A total of 166 cases suspicious for necrotizing soft tissue infection had frozen section slides available for review. Sixty-three cases were clinically determined to be positive and 103 negative. Neutrophils, necrosis, thrombi, bacteria, karyorrhexis, and fibrin were present in both positive and negative cases; however, no histological feature or combination of features was found to be both sensitive and specific for necrotizing soft tissue infection. The combined presence of necrosis and frequent neutrophils was 73% sensitive and 68% specific, with a 58% positive predictive value and 80% negative predictive value. The additional observation of bacteria decreased sensitivity to 32%, whereas raising specificity to 91%, with 69% positive predictive value and 68% negative predictive value. Thirty-two cases (19%) contained findings identified on permanent sections (eg, bacteria) not observed on frozen section slides, highlighting the risk of false negatives owing to technical limitations or sampling errors. Frozen sections in necrotizing soft tissue infections and negative cases may show similar histological findings. Combined with the risk of false negatives, these results suggest that frozen sections are likely to be of limited clinical utility due to lack of sensitivity and specificity, and risk for delayed diagnosis and treatment.
Insights
Frozen sections for necrotizing soft tissue infections show limited diagnostic accuracy. Histological features lack sensitivity and specificity, potentially delaying critical treatment for these severe infections.
Area of Science:
- Pathology
- Infectious Diseases
- Surgical Pathology
Background:
- Necrotizing soft tissue infections (NSTIs) are severe, life-threatening conditions requiring rapid diagnosis and treatment.
- Bedside or intraoperative frozen sections are proposed to expedite NSTI diagnosis and improve patient outcomes.
- Large-scale studies evaluating the diagnostic accuracy of frozen sections for NSTIs are lacking.
Purpose of the Study:
- To determine the sensitivity and specificity of frozen sections in diagnosing necrotizing soft tissue infections.
- To assess the diagnostic utility of various histological features in frozen sections for NSTIs.
Main Methods:
- A retrospective review of 166 cases suspicious for NSTI over 20 years at an academic referral center.
- Frozen section slides were evaluated for neutrophils, necrosis, thrombi, bacteria, karyorrhexis, and fibrin, blinded to the final diagnosis.
- Histological findings were compared with permanent sections and clinical outcomes (gold standard).
Main Results:
- No single histological feature or combination demonstrated high sensitivity and specificity for NSTI diagnosis.
- Necrosis with frequent neutrophils showed 73% sensitivity and 68% specificity.
- Adding bacteria observation decreased sensitivity to 32% but increased specificity to 91%.
- Nineteen percent of cases had findings on permanent sections missed on frozen sections, indicating a risk of false negatives.
Conclusions:
- Frozen sections for necrotizing soft tissue infections exhibit limited clinical utility due to insufficient sensitivity and specificity.
- Histological findings in positive and negative NSTI cases can be similar, complicating diagnosis.
- The risk of false negatives and potential for delayed diagnosis underscores the limitations of frozen sections in managing NSTIs.
