Centrifugation techniques and reagent strips in the assessment of microhaematuria

During a survey for bladder cancer in a healthy male population a surprisingly high incidence of significant microhaematuria was found and no urinary sample was completely free of blood. A study of the sensitivity of the different techniques for assessing microhaematuria seemed necessary. A semiquantitative centrifugation technique, developed for cytological purposes, was found to be the most sensitive. Blood could be detected in concentrations of less than 50 RBC/ml urine. With conventional analysis, performed carefully, the minimum detectable concentration was about 500 RBC/ml. Reagent strips, based on the orthotholidin peroxidase reaction and developed specifically for urine analysis, gave positive reactions in minimum concentrations of 1 000 000 RBC/ml (original Hemastix), 50 000 RBC/ml (new Hemastix), and 20 000 RBC/ml (Sangur-Test). Positive scores with lower concentrations could be obtained with the Sangur-Test strip when it was read with a magnifying glass. However, the degree of erythrocyturia that may be regarded as physiological and that which is pathological has yet to be defined.