Renal handling of beta 2-microglobulin in patients with cystic fibrosis.

We evaluated the renal handling of beta 2-microglobulin (beta 2-M) and creatinine in healthy outpatients (n = 6), normal children hospitalized for infections treated with antibiotics (not including an aminoglycoside) (n = 4); outpatients with cystic fibrosis (CF; n = 12), and hospitalized patients with CF (n = 6) who received a 10- to 14-day course of antibiotic treatment that included an aminoglycoside. The serum beta 2-M concentrations in the normal outpatients (2020.1 +/- 276.6 micrograms/L) were significantly lower (p less than 0.05) than those observed for outpatients (2833.3 +/- 202.6 micrograms/L) or patients with CF (2861.8 +/- 340.5 micrograms/L. There were no significant differences found for creatinine clearance or fractional excretion of beta 2-M when subjects without CF were compared with those with the disease. Furthermore, no significant differences were observed in hospitalized patients with CF when creatinine clearance and fractional excretion of beta 2-M were compared between the initiation and conclusion of aminoglycoside treatment. Glomerular filtration and proximal tubular reabsorption of beta 2-M were not altered in patients with CF. These findings do not support a global defect in proximal renal tubular reabsorption as the underlying cause for altered aminoglycoside clearance in patients with CF.