0022-534 7/78/1202-0452$02. 00/0 THE JOURNAL OF UROLOGY Copyright © 1978 by The Williams & Wilkins Co.
Vol. 120, October Printed in U.S.A.
SIGNIFICANCE OF PYURIA IN URINARY SEDIMENT MARYANNE MCGUCKIN,* LUCY COHEN
AND
ROB ROY MACGREGOR
From the Infectious Disease Section, Department of Medicine and the School of Allied Medical Professions, Department of Medical Technology, University of Pennsylvania, Philadelphia, Pennsylvania
ABSTRACT
Microscopic examination of the urinary sediment to determine the degree of pyuria is an accepted method to screen for urinary tract infection. We investigated the significance ofpyuria in relation to the method of specimen acquisition, number of white blood cells and isolation of pathogens on culture. Only 36 per cent of our patients with more than 10 white blood cells per high power field on examination of the first random specimen had more than 10 white blood cells per high power field when a repeat clean catch midstream specimen was examined, and only 20 per cent of the patients had more than 105 pathogens per ml. on culture. However, the finding of more than 10 white blood cells per high power field on a clean catch midstream specimen indicated more than 105 pathogens per ml. in 40 per cent of the cases. The use of a higher threshold for significant pyuria (more than 20 white blood cells per high power field) on examination of a random specimen increased the incidence of more than 105 bacteriuria found in specimens with initial pyuria by 43 per cent and represents the additional detection of 8. 7 per cent of the total population studied. These data indicate that when screening for pyuria and infection one should either obtain a clean catch midstream specimen for examination of urinary sediment or increase the threshold for significant pyuria on a random specimen. A presumptive diagnosis of urinary tract infection often can be made on the basis of the clinical presentation and the presence of pyuria. In 1962 Stansfeld defined pyuria as > 10 white blood cells per high power field (WBC/HPF) in the centrifuged urinary sediment. 1 In 1957 Kass, defining pyuria as 5 or more WBC/HPF, found it in almost half of his patients who had > 105 colony forming units per ml. of urine but only in 2 per cent of those with 105 colony forming units per ml. 3-6 However, pyuria may occur without bacteriuria, sometimes as a result of poor cleansing of the periurethral area before urine collection. Many physicians obtain a random voided specimen for urinalysis and microscopic examination, and then proceed to a bacteriological culture if there is significant pyuria (usually defined as >10 WBC/HPF). Since it was shown by Stansfeld and others that improper collection methods, especially in female subjects, can result in pyuria comparable to that in urinary tract infections 1•7 it would appear that a clean catch midstream specimen would give more accurate data when used for the initial microscopic examination. The same specimen could then be used for culture if indicated. The purpose of our investigation was 3-fold: 1) to determine what number of white blood cells per high power field in the routine urinalysis represented significant pyuria and would be predictive of > 105 colony forming units per ml. on culture, 2) to study whether the collection of a second urine sample (following careful instructions in the clean catch midstream specimen technique) would result in a reduction of the degree of pyuria from that found in the first random sample and 3) to evaluate a higher threshold for significant pyuria ( >20 WBC/HPF) in the random specimen. MATERIALS AND METHODS
Patients. Fifty-five patients with >10 WBC/HPF (signifiAccepted for publication January 13, 1978. * Requests for reprints: Infectious Disease Section, University of Pennsylvania School of Medicine, 555 Johnson Pavilion, Philadelphia, Pennsylvania 19104. 452
cant pyuria) and 15 patients with
Vol. 120, October Printed in U.S.A.
SIGNIFICANCE OF PYURIA IN URINARY SEDIMENT MARYANNE MCGUCKIN,* LUCY COHEN
AND
ROB ROY MACGREGOR
From the Infectious Disease Section, Department of Medicine and the School of Allied Medical Professions, Department of Medical Technology, University of Pennsylvania, Philadelphia, Pennsylvania
ABSTRACT
Microscopic examination of the urinary sediment to determine the degree of pyuria is an accepted method to screen for urinary tract infection. We investigated the significance ofpyuria in relation to the method of specimen acquisition, number of white blood cells and isolation of pathogens on culture. Only 36 per cent of our patients with more than 10 white blood cells per high power field on examination of the first random specimen had more than 10 white blood cells per high power field when a repeat clean catch midstream specimen was examined, and only 20 per cent of the patients had more than 105 pathogens per ml. on culture. However, the finding of more than 10 white blood cells per high power field on a clean catch midstream specimen indicated more than 105 pathogens per ml. in 40 per cent of the cases. The use of a higher threshold for significant pyuria (more than 20 white blood cells per high power field) on examination of a random specimen increased the incidence of more than 105 bacteriuria found in specimens with initial pyuria by 43 per cent and represents the additional detection of 8. 7 per cent of the total population studied. These data indicate that when screening for pyuria and infection one should either obtain a clean catch midstream specimen for examination of urinary sediment or increase the threshold for significant pyuria on a random specimen. A presumptive diagnosis of urinary tract infection often can be made on the basis of the clinical presentation and the presence of pyuria. In 1962 Stansfeld defined pyuria as > 10 white blood cells per high power field (WBC/HPF) in the centrifuged urinary sediment. 1 In 1957 Kass, defining pyuria as 5 or more WBC/HPF, found it in almost half of his patients who had > 105 colony forming units per ml. of urine but only in 2 per cent of those with 105 colony forming units per ml. 3-6 However, pyuria may occur without bacteriuria, sometimes as a result of poor cleansing of the periurethral area before urine collection. Many physicians obtain a random voided specimen for urinalysis and microscopic examination, and then proceed to a bacteriological culture if there is significant pyuria (usually defined as >10 WBC/HPF). Since it was shown by Stansfeld and others that improper collection methods, especially in female subjects, can result in pyuria comparable to that in urinary tract infections 1•7 it would appear that a clean catch midstream specimen would give more accurate data when used for the initial microscopic examination. The same specimen could then be used for culture if indicated. The purpose of our investigation was 3-fold: 1) to determine what number of white blood cells per high power field in the routine urinalysis represented significant pyuria and would be predictive of > 105 colony forming units per ml. on culture, 2) to study whether the collection of a second urine sample (following careful instructions in the clean catch midstream specimen technique) would result in a reduction of the degree of pyuria from that found in the first random sample and 3) to evaluate a higher threshold for significant pyuria ( >20 WBC/HPF) in the random specimen. MATERIALS AND METHODS
Patients. Fifty-five patients with >10 WBC/HPF (signifiAccepted for publication January 13, 1978. * Requests for reprints: Infectious Disease Section, University of Pennsylvania School of Medicine, 555 Johnson Pavilion, Philadelphia, Pennsylvania 19104. 452
cant pyuria) and 15 patients with
