Beta-2 microglobulin (B2M) Test

Hi,

Just like to share the information, lately patients who are on Exjade or Jadenu were routinely tested for ACR (Albumin to Creatinine Ratio). This test usually shows kidney function disruption (if any) quite late. To early detect the Kidney function, doctors have started Beta-2 macroglobulin test (normal range is 0-29).

Beta-2 microglobulin (B2M) is a protein that is found on the surface of nucleated cells (contain a nucleus) and functions as part of the human immune system. This protein is routinely shed by cells into the blood and is present in most body fluids, with highest levels in the blood, generally lower levels in spinal fluid, and trace levels in urine.

In the kidneys, B2M passes through blood-filtering units called the glomeruli and is then reabsorbed by the renal proximal tubules, structures that reclaim water, proteins, vitamins, minerals, and other vital substances. Normally, only small amounts of B2M are present in the urine, but when the renal tubules become damaged or diseased, B2M concentrations increase due to the decreased ability to reabsorb this protein. When the glomeruli in the kidneys are damaged, they are unable to filter out B2M, so the level in the blood rises.

There is a lengthy report on Incidence of deferasirox‐associated renal tubular dysfunction in children and young adults with beta‐thalassaemia at https://onlinelibrary.wiley.com/doi/full/10.1111/bjh.13002.

Damage to the renal tubes is a well known issue in thalassemics (this occurs even in thal minors, to a lesser extent), but apparently the Exjade drugs can cause the damage to increase, especially in certain classes of patients.

In conclusion, we demonstrate that asymptomatic renal tubular dysfunction was very frequent in a small cohort of predominantly oriental β‐thalassaemic patients who receive deferasirox; they are much more likely to develop renal tubular dysfunction with concomitant metabolic acidosis and electrolyte disturbances when compared to patients on other chelation regimens. If discovered early, it is reversible with either dosage reduction or withholding treatment. Vigilant monitoring of renal tubular dysfunction and serum electrolyte levels is recommended in patients who receive deferasirox therapy.

Thanks Andy. Little Miss A results are critically high for Beta-2macroglobulin test. Her number is 3000 compared to normal range of 0-29 (test done in Dec 2018). The ACR values are mildly high at 3.9 compared to normal range of 1-3.5

This early deduction test (B2M) just started as of December 2018. She is off Jadenu for the last two months, we are waiting for the result of repeat test soon. Will keep posted.