In which case would eGFR from plasma creatinine be more accurate than plasma cystatin C?

The most accurate estimation of Glomerular Filtration Rate (eGFR) using plasma creatinine occurs in the context of a post-renal transplant patient. In this situation, plasma creatinine levels can provide a more reliable assessment of kidney function due to the stabilization of kidney function post-transplant, as the graft begins to function properly.

Plasma creatinine is influenced by muscle mass and hydration status, which can vary significantly in other conditions but is generally more consistent in well-managed transplant patients. In the early period following transplant, the dynamics of renal function can be closely monitored and the influence of the transplant on creatinine levels can lead to a clearer picture of kidney performance.

In contrast, plasma cystatin C might be less reliable in this context, especially immediately after a transplant or during recovery, as its levels can be affected by factors such as inflammation or changes in tissue turnover. Hence, plasma creatinine-derived eGFR is favored in evaluating kidney function for post-renal transplant patients, as it is more reflective of the actual filtration capacity in that scenario.