If a choice has to be made between serum or urine tests, then the use of serum is clearly preferable for the many reasons given above and summarised in Table 24.2 . When both serum and urine tests are available, it is clinically reassuring to have two separate tests. Clearly, samples do occasionally get incorrectly analysed, mislabelled or misplaced, so supporting evidence for making a diagnosis or changing treatment is always helpful. In the context of a stem cell transplant in MM patients, for example, the additional cost of performing both serum and urine tests is inconsequential.
|Serum versus urine measurements|
|Easy to collect||Difficult to collect|
|κ/λ ratio less affected by renal function||Renal function affects levels|
|Easily analysed||Samples may need concentrating|
|Easily stored||More difficult to store|
|More frequently abnormal in NSMM and AL amyloidosis||Less frequently abnormal|
|More sensitive for monitoring patients|| Less sensitive for monitoring patients|
Table 24.2. Summary of clinical and analytical comparisons of sFLC and urine electrophoresis tests .