From the Guidelines
The presence of 0-3 white blood cells (WBC) in urinalysis is generally considered insignificant and not indicative of a urinary tract infection (UTI).
Significance of WBC in Urinalysis
- A significant pyuria is defined as ≥10 white blood cells/mm3 on an “enhanced urinalysis” or ≥5 white blood cells per high power field on a centrifuged specimen of urine or any leukocyte esterase on a dipstick 1.
- The presence of 0-3 WBC in urinalysis does not meet this criteria, suggesting that it is unlikely to be associated with a UTI.
- The American Academy of Pediatrics and the Infectious Diseases Society of America recommend that urinalysis and urine cultures should only be performed in patients with symptoms of UTI, such as fever, dysuria, or gross hematuria 1.
- In patients with long-term indwelling urethral catheters, evaluation is indicated if there is suspected urosepsis, especially in the context of recent catheter obstruction or change 1.
- The minimum laboratory evaluation for suspected UTI should include urinalysis for determination of leukocyte esterase and nitrite level by use of a dipstick and a microscopic examination for WBCs 1.
- If pyuria (≥10 WBCs/high-power field or a positive leukocyte esterase or nitrite test is present on dipstick, only then should a urine culture (with antimicrobial susceptibility testing) be ordered 1.
From the Research
Significance of 0-3 White Blood Cells in Urinalysis
- The presence of 0-3 white blood cells (WBC) in urinalysis is generally considered to be within the normal range, indicating the absence of a urinary tract infection (UTI) 2.
- A study published in JAMA found that uninfected urine usually contained less than or equal to 10^3 WBCs per milliliter, although up to 8 x 10^3 WBCs per milliliter were observed in some cases 2.
- Another study published in The Journal of Emergency Medicine found that patients with pyuria (defined as >10 WBC/HPF) were more likely to have a positive urine culture, but the presence of 0-3 WBC/HPF was not specifically associated with an increased risk of UTI 3.
- A study published in Cureus found that the sensitivity and specificity of WBC in dipstick urinalysis were 62.7% and 100%, respectively, indicating that the presence of WBC is a strong indicator of UTI, but the absence of WBC does not necessarily rule out the possibility of UTI 4.
- Studies in pediatric populations have found that the optimal urine WBC threshold for predicting UTI varies depending on the concentration of the urine, with thresholds ranging from 3 WBC/HPF in dilute urine to 6 WBC/HPF in concentrated urine 5, 6.
Implications of 0-3 WBC in Urinalysis
- The presence of 0-3 WBC in urinalysis may not be sufficient to rule out the possibility of UTI, particularly in patients with symptoms or risk factors for UTI 3, 4.
- Further testing, such as urine culture, may be necessary to confirm the diagnosis of UTI in patients with 0-3 WBC in urinalysis 2, 3, 4.
- The interpretation of urinalysis results should take into account the clinical context and the presence of other symptoms or risk factors for UTI 5, 6.