Urinary Protein Bound Sialic Acid Differentiates Steroid-Sensitive And Steroid-Resistant Nephrotic Patients
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Urinary Protein Bound Sialic Acid (UPBSA) is Used to Differentiate Between Steroid Sensitive and Steroid Resistant Nephrotic Patients
Protein estimation index failed to differentiate the steroid sensitive nephrotic syndrome (SSNS) patients from the steroid resistant nephrotic syndrome (SRNS) patients. Sialic acid, which is a negatively charged sugar moiety attached to the proteins can be used to differentiate the SSNS and the SRNS patients.
Aim of the study
The aim of the study was to differentiate between steroid sensitive and steroid resistant nephrotic syndrome (NS) patients by assaying the urinary protein-bound sialic acid (UPBSA) levels and to know the clinical importance of UPBSA in nephritic patients
The study included the children with first-onset of nephritic syndrome.
The study excluded the children having chronic renal failure during the time of sample collection.
The study involved 70 nephrotic syndrome patients with in the age group of 1-8 years. Out of this population, 47 were SSNS patients and 23 were SRNS patients. The urine samples were collected before the corticosteroid treatment as well as during and after the treatment for 18 weeks. The urine samples were assayed for UPBSA by using Aminoff’s method. Results were analyzed by unpaired student t test. Receiver – operating curve was drawn to determine the cutoff for differentiation of SSNS and SRNS.
Urine samples of 100ml were collected from nephrotic syndrome patients before the corticosteroid therapy initiation. Steroid resistant (SR) patients were partly diagnosed by histopathology.
Urine samples were centrifuged with trichloroacetic acid which caused the precipitation of the protein. This protein was stored at -50˚C; it was assayed and estimated by Aminoff’s method. The procedure was continued for 18 weeks after the steroid treatment and the children were differentiated as SSNS and SRNS.
- Patients with response to steroid therapy and minimal or nil proteinuria were grouped as SSNS.
- Children with no response to the therapy and with proteinuria (2+ or greater) even after 8 weeks of steroid treatment were grouped as SRNS.
Parameters to be measured
Urinary protein bound sialic acid in urine
The urinary protein bound sialic acid was 2.1 in SSNS and 3.92 in SRNS children. The cutoff value of UPBSA was 2.71 of protein with sensitivity of 75% and specificity of 75.5%.
Sialic acid is a 9 carbon containing negatively charged carbohydrate. This sugar contributes negative charges to the proteins in the plasma which can be used as a marker for the differentiation of SSNS and SRNS patients.
The estimation of UPBSA helps to differentiate the SRNS from the SSNS patients, without waiting for the results to be shown at the end of the steroid therapy.
The patients who are not responding to the steroid therapy can thus be given alternate medication for better effect.
Niranjan Gopal et. al (2016). Assay of Urinary Protein-Bound Sialic Acid can Differentiate Steroid-Sensitive Nephrotic Syndrome from Steroid-Resistant Cases. Saudi J Kidney Dis Transpl. 2016 Jan;27(1):37-40.
Available at http://www.ncbi.nlm.nih.gov/pubmed/26787564/
- Urinary protein bound siliac acid final
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