proteintocreatinine

Protein-to-creatinine ratio, commonly abbreviated PCR, is a laboratory measure used to estimate the amount of protein being excreted in urine from a single spot sample. It provides an approximation of daily protein excretion and is frequently used to screen for and monitor proteinuria, a potential sign of kidney disease. PCR is typically reported as milligrams of protein per milligram of creatinine, or more often as milligrams of protein per gram of creatinine in routine clinical reporting.

Measurement and interpretation rely on testing a random urine sample for both total protein and creatinine. The ratio of protein concentration to creatinine concentration is calculated, and this value is then interpreted against the laboratory’s reference ranges. Because creatinine production varies with muscle mass and other factors, PCR is most reliable when compared with prior results from the same patient or when interpreted alongside clinical context. In many settings, a spot PCR correlates reasonably well with 24-hour urine protein excretion and can reduce the need for cumbersome 24-hour collections, though some situations may still require a timed collection for precise quantification. For detecting albumin specifically, the albumin-to-creatinine ratio (ACR) is often preferred, as it is more sensitive to small amounts of albumin.

Clinical use includes initial screening for proteinuria, assessment of kidney disease progression, and monitoring response to therapy in conditions such as diabetes and hypertension. Limitations include variability due to hydration, recent exercise, diet, and differences in muscle mass, which can influence creatinine production and thus the ratio. Repeated testing is commonly recommended to confirm persistent proteinuria.