Journal Article

Targeted urine microscopy in Anderson-Fabry Disease: a cheap, sensitive and specific diagnostic technique

Mathu Selvarajah, Kathy Nicholls, Tim D. Hewitson and Gavin J. Becker

in Nephrology Dialysis Transplantation

Published on behalf of European Renal Association - European Dialysis and Transplant Assoc

Volume 26, issue 10, pages 3195-3202
Published in print October 2011 | ISSN: 0931-0509
Published online March 2011 | e-ISSN: 1460-2385 | DOI: http://dx.doi.org/10.1093/ndt/gfr084
Targeted urine microscopy in Anderson-Fabry Disease: a cheap, sensitive and specific diagnostic technique

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Background. Anderson-Fabry disease (AFD) is an X-linked lysosomal storage disorder resulting from the deficiency of trihexosylceramide α-galactosidase (α-Gal A). The diagnosis is often missed or delayed, and specific diagnostic tests (serum α-Gal A activity, genotyping or biopsy) are expensive and not widely available. We evaluated the diagnostic potential of urine microscopy in AFD.

Methods. We studied 35 male and female AFD patients across a wide phenotypic spectrum and 21 controls with other renal diseases. Fresh urine sediment was examined under phase-contrast microscopy using polarized light for Maltese cross (MC) particles, anti-CD77 antibody to detect globotriaosylceramide (GL3, the substrate of α-Gal A), and anti-podocalyxin antibody to assess podocyte excretion.

Results. Characteristic MC 2 particles and anti-CD77 binding within vacuolated urinary epithelial cells were both detected in AFD with high sensitivity and specificity (MC 2 detection sensitivity 100%, 95% confidence interval (CI) 85.4–100%, specificity 100%, CI 80.8–100%; anti-CD77-binding sensitivity 97.1%, CI 83.3–99.9, specificity 100%, CI 80.8–100%). Albuminuria (urinary albumin-to-creatinine ratio, ACR) correlated with quantitative particle excretion—in low, intermediate and high MC excretors, and median ACR was 1.6, 6.9 and 20.0 mg/μmol, respectively (analysis of variance P = 0.017). Podocyte staining was positive in ∼50% of all AFD patients and was similar in those with and without clinical Fabry nephropathy (FN), whether or not treated with enzyme replacement.

Conclusions. Targeted urinary microscopy is a non-invasive, inexpensive, accessible and rapid diagnostic technique, especially applicable where serum α-Gal A activity and genotyping are not affordable or available. As the number of urinary MC 2 particles increases with rising albuminuria, the technique may also be useful in assessing FN burden.

Keywords: fabry disease; GL3; urinary microscopy; CD77; podocyte excretion

Journal Article.  4649 words.  Illustrated.

Subjects: Nephrology

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