Conversely, microscopic examination of urine for WBCs and bacteria provides direct evidence of their presence, but there are varying standards and techniques. WBCs have been counted per high power field and in others per cubic milliliter. With these variations in technique, it is not surprising that there have been inconsistencies in those studies evaluating the microscopic examination of urine. Several recent studies have evaluated the individual components of urinalysis and compared them with the results of bacterial cultures in pediatric populations. A high negative predictive value is extremely useful as it helps to decide which urine samples to culture and which to discard.
Debate continues regarding the best age at which to test a child.
Theoretically, younger children and infants should be the best candidates for screening on the assumption that such screening would avert early renal scar formation. Adhesive polyethylene bag specimens remain the kindest choice but have an unacceptable contamination rate. Straight catheterization and suprapubic aspiration of the bladder are options when a UTI is highly suspected. The cost of screening is significant. These charges did not include physician costs, medications, diagnostic imaging and days lost from work or school.