A new challenge for urinary free light chains: assessment of the upper reference limit in healthy subjects.

OBJECTIVE: Free light chains (FLCs) can be measured in both urine (uFLC) and serum (sFLC) in immunochemistry. We aim to compare FLC levels in serum and urine assessed among healthy volunteers and measured upper reference limits (URLs) of urinary FLC to creatinine ratio (uFLC/uCr) in mg/g to compare with the manufacturer's recommended URLs. PATIENTS AND METHODS: Eligibility criteria: normal serum and urine FLC measure and negative serum/urinary immunofixation. Immunoturbidimetry was used to assess both κ and λ FLCs. The URLs were calculated with the 97.5th percentile of uFLC concentrations according to the Clinical and Laboratory Standards Institute recommendations. RESULTS: 126 healthy subjects (median age 46 years, 62% females) met the inclusion criteria. Median concentrations of κ and λ sFLCs were similar both for males and females without significant differences. κ and λ uFLCs were significantly higher in males than in females (p < 0.001 and p = 0.004, respectively). Slower clearance for λ FLC compared to κ FLC was observed with an increased κ/λ uFLC ratio in both males and females. URLs for male and female subjects: κ uFLC mg/g uCr = 34.35 vs. 23.18, and λ uFLC mg/g uCr = 3.59 vs. 1.96, respectively compared well with manufacturer's URLs. CONCLUSIONS: FLC catabolism is gender-dependent and occurs less rapidly in λ FLC than in κ FLC. The determination of the URL of uFLC, as uFLC/uCr, in healthy subjects in morning urine, proved to be consistent with the manufacturer's recommendations, but with a significant difference according to gender.

An approach to realistic evaluation of antihypertensive regimes.

Where practicable, all subjects found with onset-phase-four blood pressure of 90 mmHg or more after referral were allocated, on a random basis, to alternative antihypertensive regimes at a dosage related to response. Of those 110 receiving either guanethidine, methyldopa or debrisoquine, only the group on methyldopa had significantly reduced median blood pressure by two out of four criteria and after 6 months of therapy. It is nevertheless considered that by assessment of the total group more significant conclusions can be drawn for an eventual attempt to control hypertension on a community basis than by studies of highly selected groups treated under unusually favourable conditions.