Concordance of diagnostic modalities in atypical skin and soft tissue infections in hospitalized patients.

Skin and soft tissue infections (SSTIs) have high rates of morbidity and mortality worldwide but lack reliable standards for diagnostic workup. As a result, atypical infections, more prevalent among immunocompromised patients, can be missed due to deviance from classic features only to be revealed later through inconsistently performed ancillary studies. Our objectives included to evaluate the sensitivities of clinical impression, histopathology, tissue culture, and molecular and non-molecular ancillary tests in diagnosing inpatient SSTIs, as well as to qualitatively discuss the unusual features making a subset of infections "atypical." To do so, we retrospectively reviewed the histopathologic reports and charts of inpatient dermatologic consults at a single tertiary care institution over a 3-year period. We identified a total of 111 cases of SSTIs evaluated by the inpatient dermatology consultation service with concurrent skin or soft tissue biopsy, with 32.4% representing atypical infections. Among these, clinical impression suggested infection in 9(25.0%), routine histopathology in 21(58.3%), specialized stains for microorganisms in 22(68.8%), and tissue culture in 15(68.2%). Due to incomplete picture that each modality by itself creates, we conclude that clinicians and pathologists should carry a low threshold for including SSTIs in their differential diagnoses and should evaluate with skin biopsy, special stains for microorganisms, and ancillary studies, particularly in critically ill individuals who necessitate timely diagnoses.