RESUMO
BACKGROUND: Our aim was to establish local reference intervals for k and λ free light chains. METHODS: Fresh sera from 246 healthy blood donors were analyzed to evaluate reference intervals for FLC. CLSI EP28-A3C protocol was applied to establish new RIs. RESULTS: The 95% reference interval for FLCk was 7.20 - 20.0 mg/L, and that for FLCλ was 6.72 - 20.23 mg/L. The diagnostic interval for the k/λ ratio was 0.5 - 2.11 mg/L. When we analyze the distribution of the k/λ ratio results for the 1,025 pieces of data collected using the diagnostic intervals reported by the manufacturer and those established in this study, we observed that discordant results were reported in 14.5% of patients with MGUS and 16.3% of patients with multiple myeloma. CONCLUSIONS: Our findings underline the importance of establishing the reference intervals for serum FLCs and the proper diagnostic interval by instrument platform and appropriate to the target study patient population.