CBC
Chem
PT/PTT/INR
CK
Lactate
Surgical exploration is the ONLY way to definitively establish the diagnosis of<unk>  infection
Imaging
Should not delay surgical exploration
CT is study of choice - soft tissue gas, edema and fluid collections, fascial thickening with fat stranding
US may show thickened fascial planes, fluid between fascial planes, irregularity of the fascia, subcutaneous emphysema. The study may be limited by soft tissue gas. Video lecture.
MRI - T2 subcutaneous, intramuscular, and fascial edema
Absence of gas on imaging does not exclude diagnosis, as gas may be occult and/or certain organisms do not classically produce gas (i.e. Group A Strep)
Should not delay surgical exploration
CT is study of choice - soft tissue gas, edema and fluid collections, fascial thickening with fat stranding
US may show thickened fascial planes, fluid between fascial planes, irregularity of the fascia, subcutaneous emphysema. The study may be limited by soft tissue gas. Video lecture.
MRI - T2 subcutaneous, intramuscular, and fascial edema
Has not been prospectively validated, index of suspicion is key and 10% of the patients with a score < 6 had<unk> . A score > 6 has PPV of 92% and NPV of 96% for<unk> .
<15: 0 points
15–25: 1 point
>25: 2 points
>13.5: 0 points
11–13.5: 1 point
<11: 2 points
Low Risk: score 5 (10% of pts with score < 6 still had nec fasc)
Moderate Risk: score 6– 7
High Risk: score >8
Proposed algorithm
Retrospective study discovered:
WBC count >15.4(x103/mm3) OR Na <135(mmol/L)
Associated with<unk>  and combo of both increased likelihood of<unk> 
PPV 26%/NPV 99%
Useful tool to rule out<unk> , not a good tool for confirming presence of<unk> 
Helps distinguish<unk>  from non-NF infection, when classic 'hard' signs of<unk>  are absent however clinical judgment should still be used in patient with high suspicion of the disease
WBC count >15.4(x103/mm3) OR Na <135(mmol/L)
Associated with<unk>  and combo of both increased likelihood of<unk> 
PPV 26%/NPV 99%
Helps distinguish<unk>  from non-NF infection, when classic 'hard' signs of<unk>  are absent however clinical judgment should still be used in patient with high suspicion of the disease
Necrotizing fasciitis
Cellulitis
Necrotizing cellulitis
Hand cellulitis
Wet gangrene
Facial cellulitis
Plantar fasciitis
Orbital cellulitis