The correct answer is C. Serum bicarbonate.

The development of desquamation and blistering 10 days after initiation of antibiotics is very highly suspicious for toxic epidermal necrolysis. Usually, due to sulfonamide antibiotics, this condition can be prognosticated with a variety of measures, such as SCORTEN or ABCD-10. Serum bicarbonate has been shown to be the most important factor in these scales.

Body surface area involvement and heart rate are also in the SCORTEN scoring system but are not the greatest predictors of mortality. Temperature and urine glucose are not involved in the SCORTEN scoring system.

References

Yeong EK, Lee CH, Hu FC, M Z W. Serum bicarbonate as a marker to predict mortality in toxic epidermal necrolysis. J Intensive Care Med. 2011;26(4):250-254.