The investigators prepared a power calculation using a Wilcoxon rank sum test. Assuming an estimated standard deviation of 4.6 ng/ml and a mean of 9.9 ng/ml, the investigators will need to include a maximum of 150 NSTI patients and 50 elective surgery patients to reach a statistical power of at the very least 60 % (a very conservative estimate) and presumably closer to 85 % (more realistic estimate) at a 5 % significance level. The estimates depend on data distribution.