Kappa/lambda ratio

0.26 to 1.65 is the range for the most widely used UK method (Freelite). Many laboratories print a wider range, 0.37 to 3.1, for people with reduced kidney function, because the kidneys clear kappa faster than lambda and the ratio drifts upwards as they fail.

This is the free kappa light chain level divided by the free lambda level. Healthy antibody-producing cells make a mixture of the two, so the ratio stays within a narrow band even when both are high, for example with inflammation or kidney disease. When a single clone of cells is producing one type only, the ratio moves away from that band, which is why it is the most useful of the three light chain figures.

Doctors read it, together with the two light chain values and serum protein electrophoresis, when looking at myeloma and related conditions and when following people with a known light chain condition over time.

• Myeloma and related conditions that make kappa light chains
• Reduced kidney function, which nudges the ratio upwards because kappa is cleared faster than lambda
• Some rare conditions where lambda-producing cells are suppressed

• Myeloma and related conditions that make lambda light chains
• Treatment of a kappa light chain condition, bringing the ratio back towards the band
• Some rare conditions where kappa-producing cells are suppressed

• Reduced kidney function shifts the ratio upwards without any blood condition, which is why a wider range is used then
• Because it is a ratio, a small error in a very low lambda value moves it a great deal
• Methods differ, so a ratio from one laboratory is not directly comparable with another's

No fasting needed. It is calculated from the two light chain values on the same report and is read with kidney function in mind. In people with a known condition the trend over time matters more than one value.

Written by a UK consultant physician. Typical UK adult reference ranges; your laboratory's own printed range takes precedence.