Abstract - THE ADVANTAGES OF PHASE CONTRAST MICROSCOPY IN URINE SEDIMENT INVESTIGATION
Tünde Kránicz, MSc
77 Elektronika Ltd, Budapest, Hungary
Urinalysis is one of the most common and most important tests for screening urinary tract and kidney diseases. The presence or absence of urinary sediment particles is crucial for the diagnosis of such diseases. In the routine urine sediment investigation by manual microscopy the bright-field illumination is the most wide-spread, even though phase contrast illumination improves the recognition of several particle types. Phase contrast microscopy is an optical microscopy technique that converts phase shifts in light passing through a transparent specimen to brightness changes in the image. Phase shifts themselves are invisible, but become visible when shown as brightness variations. In particular, for urinary sediment examination, phase contrast supplies an optimal identification of particles with a low refractive index (e.g., hyaline casts and RBC devoid of their haemoglobin content, the so-called “ghost RBC”) and of cellular morphological details. This last feature is of the highest importance for the differentiation of the renal epithelial cells from transitional epithelial cells. Moreover, it offers the best approach for the evaluation of RBC morphology, therefore the use of phase contrast microscopy is encouraged also by international guidelines on urinalysis. As a consequence of the advantages, phase contrast technology is more widespread both in manual microscopy and automated urinalysis systems all around the world.