Abstract
BackgroundEffective management of trauma-related invasive fungal wound infections (IFIs) depends on early diagnosis and timely initiation of treatment. We evaluated the utility of routine staining, histochemical stains and frozen section for fungal element identification.MethodsA total of 383 histopathological specimens collected from 66 combat-injured United States military personnel with IFIs were independently reviewed by two pathologists. Both periodic acid-Schiff (PAS) and Gomori methenamine silver (GMS) stains were used on 74 specimens. The performance of the two special stains was compared against the finding of fungal elements via any histopathological method (ie, special stains or hematoxylin and eosin). In addition, the findings from frozen sections were compared against permanent sections.ResultsThe GMS and PAS results were 84 % concordant (95 % confidence interval: 70 to 97 %). The false negative rate of fungal detection was 15 % for GMS and 44 % for PAS, suggesting that GMS was more sensitive; however, neither stain was statistically significantly superior for identifying fungal elements (p = 0.38). Moreover, 147 specimens had frozen sections performed, of which there was 87 % correlation with permanent sections (60 % sensitivity and 98 % specificity). In 27 permanent sections, corresponding cultures were available for comparison and 85 % concordance in general species identification was reported.ConclusionsThe use of both stains does not have an added benefit for identifying fungal elements. Furthermore, while the high specificity of frozen section may aid in timely IFI diagnoses, it should not be used as a stand-alone method to guide therapy due to its low sensitivity.
Highlights
Effective management of trauma-related invasive fungal wound infections (IFIs) depends on early diagnosis and timely initiation of treatment
Patient demographics and injury characteristics From the population of wounded U.S military personnel admitted to Landstuhl Regional Medical Center (LRMC) (June 2009 - August 2011), 66 Invasive fungal wound infections (IFI) patients met the criteria for inclusion in the study population
Tissue specimens were examined in separate study population subset analyses based on the following criteria (Fig. 1): stained with both periodic acid-Schiff (PAS) and Gomori methenamine silver (GMS) (Analysis 1); having aseptate or septate organisms identified on permanent sections (Analysis 2); and having frozen sections available (Analysis 3)
Summary
Effective management of trauma-related invasive fungal wound infections (IFIs) depends on early diagnosis and timely initiation of treatment. If an IFI is suspected, but organisms are either not identified or are poorly visualized with H&E, the use of additional stains, Gomori methenamine silver (GMS) and/or periodic acid-Schiff (PAS), can be used to either rule out a fungal infection or identify morphologic characteristics. Both GMS and PAS stains provide greater contrast by highlighting the fungal cell wall; misidentification, false-positives and false-negatives, do occur with these techniques. When PAS is used, background tissue components may be stained along with the fungal cell wall [9, 16]
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