The plasma phenolsulfonphthalein index (PSPI) of renal function. II. Correlation with other parameters of renal function and indications for use.

The plasma phenolsulfonphthalein index (PSPI) was determined in 175 subjects and was compared with levels of blood urea nitrogen (BUN) and serum creatinine, 15-minute urinary excretion of PSP, and clearance of creatinine, PAH and inulin. Statistical analyses indicate that the PSPI measures the same function as the 15-minute urine test when PSP is administered in a dosage of 1 mg./kg. body weight; and that, although the index cannot be used as a precise substitute for PAH clearance, it is equally repeatable and no greater error is associated with its measurement. The PSPI has been found of most value when complete, accurately timed urine collections are unobtainable because of urological abnormality or inability of the patient to co-operate.