[Clinical value of studying hematuria using phase-contrast microscopy]

To evaluate the examination of urine erythrocytes with a contrast phase microscope for the etiological diagnosis of haematuria (erythrocytes > 10/mm3 of non centrifuged urine) the charts of 84 patients with haematuria were reviewed. A nephrological origin had been established with certainty in 56 cases with a renal biopsy and an urological origin was also established with certainty in 28 cases thanks to appropriate radiological, endoscopical and pathological examinations. The morphological criteria of the erythrocytes deformation were those of Birch and Fairley but the quantitative criteria of these authors (either 80 or 100%) were found to be of no value. By successive approaches the threshold of 20% of deformed erythrocytes was selected and found to be the best criterion for diagnosing glomerular hematuria: the sensitivity of the test is then 73% and its specificity 60%. As these results were relatively modest, conditions which decrease the percentage of deformed erythrocytes were excluded to improve the sensitivity, such as macroscopic haematuria and also examinations made during the 6 hours following furosemide administration whereas conditions which increase the percentage of deformed erythrocytes and which are easily diagnosed such as urinary infections, lithiasis and renal insufficiency associated with an uropathy were excluded in order to improve the specificity. Then the examination has a sensitivity and a specificity of 90% which makes it clinically relevant, authorizing a wait and see attitude in case there is an isolated microscopic haematuria of glomerular type.