Table 1.

Twenty-four-hour FLC clearances for κ and λ in relation to normal (Crea−) or pathologically increased (Crea+) serum creatinine levels (>1.17 mg/dL for males and >0.95 mg/dL for females) and the results of serum FLC assays and urine IFE tests

IsotypeSample groupsNormal serum creatinine FLC clearance (L/24 h)
Abnormal serum creatinine FLC clearance (L/24 h)
nMedian (range)nMedian (range)
κ MMFLC−BJP−1051.75 (0.21-57.06)*587.79 (0.22-42.89)*
FLC+BJP−320.70 (0.004-11.47)**163.06 (0.36-18.27)††
FLC+BJP+287.58 (0.34-634.95)**221.65 (0.29-99.65)††
FLC−BJP+733.15 (4.52-76.44)1
λ MMFLC−BJP−1050.71 (0.04-13.91)§581.04 (0.10-11.08)§
FLC+BJP−480.24 (0.02-8.39)‡‡210.86 (0.02-4.65)§§
FLC+BJP+253.77 (0.52-70.27)‡‡121.57 (0.10-6.49)§§
FLC−BJP+1
  • NOTE: Twenty-four-hour FLC clearance was calculated as the ratio of 24-hour urinary excretion for κ or λ to the respective serum concentration using the following formula: 24-hour clearance (L/24 hours) = urine FLC (mg/24 hours) / serum FLC (mg/L). The FLC clearance represents the volume of plasma that contained the measured FLC excreted in the urine per unit time. In sFLC+uBJP+ samples, the 24-hour clearances were significantly higher than in sFLC+uBJP− samples, both for κ and λ, when they were associated with Crea−. In sFLC+uBJP− samples, the 24-hour clearances were significantly higher in samples with Crea+ than Crea−, but only for κ. In sFLC+uBJP+ samples, the 24 clearances were significantly lower in Crea+ than Crea− samples, both for κ and λ. In sFLC−uBJP− samples, there were significantly higher 24-hour clearances in Crea+ than Crea− samples, both for κ and λ. The group of sFLC−uBJP+ samples had the highest 24-hour clearances for FLC κ observed.

    Abbreviations: MM, multiple myeloma; sFLC−, negative serum FLC κ/λ ratios; sFLC+, positive serum FLC κ/λ ratios; uBJP−, negative urine IFE tests; uBJP+, positive urine IFE tests.

  • * versus *, P = 0.001;

  • versus †, P = 0.006;

  • versus ‡, P = 0.044;

  • § versus §, P = 0.035;

  • versus ∥, P = 0.257;

  • versus ¶, P = 0.016;

  • ** versus **, P = 0.0001;

  • †† versus ††, P = 0.609;

  • ‡‡ versus ‡‡, P = 0.0001;

  • §§ versus §§, P = 0.0578.