Renal Function Immunoassay Tests

Precision testing for renal health

Overview

Renal Function impairment

Kidney function can be assessed by using markers such as creatinine to calculate the estimated Glomerular Filtration Rate (eGFR).

Proteinuria is the presence of excess proteins in urine and can be assessed by performing several urine tests. Undetected proteinuria may mean underlying kidney damage is not identified. This may mean that irreversible kidney damage can occur, leading to kidney failure.

Renal impairment in Multiple Myeloma (MM):

  • Renal impairment ([eGFR] of <60 ml/min/1.73 m2) is a common and potentially serious finding in Multiple Myeloma
  • Newly diagnosed MM patients with renal impairment have inferior survival rates
  • Early diagnosis and prompt treatment of renal impairment due to cast nephropathy caused by multiple myeloma is critical since the window of opportunity for reversing it is very limited
  • Patients with severe acute kidney injury (AKI) of unknown cause should be screened for monoclonal gammopathy in case this is the underlying cause of the kidney injury
Several assays available on the Optilite® Analyser can be used to assess kidney function, and detect proteinuria, using serum and urine samples

Renal Funtion assessment

Why choose cystatin measurement OVER creatinine when calculating estimated glomerular filtration rate?

Assessment of renal function is vital in Multiple Myeloma (MM) patients. This is often done by estimating glomerular filtration rate (eGFR).  This calculation can use creatinine or Cystatin C values in the estimate. Use of creatinine in the calculation may underestimate the extent of kidney disease in patients with MM, which can affect treatment doses and toxicity.

Compared to creatinine, Cystatin C test is a more sensitive marker for renal filtration and is unaffected by age, gender, or race1,2. The use of Cystatin C to calculate eGFR instead of creatinine may help avoid underestimating kidney disease in MM patients, particularly among women.

A recent study in newly diagnosed patients with MM [24 women / 37 men, mean age of 68 (±11)] investigated different equations used for the evaluation of eGFR, and compared them with the reference method to identify the most sensitive equation for detection of kidney disease, and to identify patients with more risk factors.3

The study concluded that inclusion of Cystatin C values in equations such as CKD-EPI and CAPA are more accurate when detecting hidden kidney disease, as well as patients with more and worse prognostic factors.

There is evidence that Cystatin C is superior to creatinine when calculating eGFR for patients with MM

Cystatin C – Recommended for the assessment of patients with Multiple Myeloma

National Kidney Foundation – American Society of Nephrology  (NKF-ASN) recommendations: 

A joint task force of NKF- ASN recommended immediate implementation of CKD-EPI creatinine equation; issued a report aiming at suppressing race adjustments in eGFR calculations, and stressing that Cystatin C-based calculations do not include such bias4

 

  • β2 microglobulin is a low molecular weight protein found on the surface of most nucleated cells
  • It is excreted only in trace amounts in the urine. However, in tubulo-interstitial disorders, excretion of this protein increases markedly. Thus, urinary β2-microglobulin measurement is a valuable tool for associated with tubulo-interstitial renal damage
  • Optilite β2 microglobulin urine kit is used for quantitative determination of beta-2 macroglobulin in urine samples. This aids in the diagnosis of active rheumatoid arthritis and kidney disease
  • β2-microglobulin levels in serum are typically raised in renal disease and rheumatoid arthritis
  • Elevated serum levels are also observed in inflammatory conditions and haematological malignancies
  • Optilite β2 microglobulin kit is used for quantitative determination of beta-2 macroglobulin in serum or plasma (lithium heparin, or EDTA plasma) samples. This aids in the diagnosis of active rheumatoid arthritis and kidney disease
  • Alpha-1-microglobulin (A1M) is a small protein that is synthesized mainly by the liver cells and readily binds with serum immunoglobulin A. Due to its small size, the unbound form is freely filtered through the glomerulus and is reabsorbed by proximal tubular cells
  • Proximal tubular injury can compromise tubular reabsorption and increase levels of alpha-1-microglobulin in urine. Increased A1M is an early sign of renal damage at the proximal tubular level
  • Optilite alpha-1-microglobulin kit is used for quantitative determination of A1M levels in urine and assess proximal tubular function and proteinuria
  • Alpha -2- Macroglobulin (α2M) is a high molecular weight glycoprotein found in the blood. Due to its large size, it is not filtered by the glomerulus and hence is normally not present in urine
  • The presence of α2M in the urine helps in the differentiation of glomerular and post-renal haematuria, especially when albumin levels are greater than 100mg/L
  • Optilite Alpha -2- Macroglobulin kit is used for quantitative determination of α2M levels in urine. The measurement of α2M in urine is useful in the diagnosis of post-renal haematuria
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References
1. LATERZA OF, PRICE CP, SCOTT MG. CYSTATIN C: AN IMPROVED ESTIMATOR OF GLOMERULAR FILTRATION RATE? CLIN CHEM 2002;48:699-707.
2. INKER LA, ENEANYA ND, CORESH J, TIGHIOUART H, WANG D, SANG Y, ET AL. NEW CREATININE- AND CYSTATIN C-BASED EQUATIONS TO ESTIMATE GFR WITHOUT RACE. N ENGL J MED 2021;385:1737-49.
3. Cepeda-Piorno et al. Cystatin C-Based Equations Detect Hidden Kidney Disease and Poor Prognosis in Newly Diagnosed Patients with Multiple Myeloma. Adv Hematol 2022
4. Delgado C et al. A Unifying Approach for GFR Estimation: Recommendations of the NKF-ASN Task Force on Reassessing the Inclusion of Race in Diagnosing Kidney Disease. Am J Kidney Dis. 2022;79(2):268-288.e1.