Is Pyuria Necessary to Diagnose Pediatric UTI?
Howard Uman, MD Pediatrician An Answer to Joe Breuner
3-month-old female with fever >102, no localizing source. Workup: UA (–), UC (+) >100,000 E coli WBC 20, 75% PMN; blood culture (-),CRP 10 “10% of infants with pyelonephritis have no pyuria”
? Early in course ? Inadequate time to mild inflammatory response ? “Immaturity of inflammatory response” Finding a reliable model…
“diagnostic accuracy of the urinalysis for urinary tract infection in infants <3 months of age,” Shroeder, et al, pediatrics volume 135, #6, June 2015, PE. 965–971. Sample: “True UTI”—urosepsis with (+)UC + (+)BC (vs NOT “asymptomatic bacteriuria”) Invasion of renal parenchymabacterial multiply invade bloodstream Damage occurs as a byproduct of the body’s own inflammatory response Findings from Schroeder, 2016
“pyuria is a reliable finding in “true UTI” Pyuria present in 96–99.5% “UA sensitivity in bacteremic UTI is higher than previous reports in infants with UTI in general…”: >99% sensitivity for pyuria and/or LE With UC(-): 87.8% LE (-) and WBC (-) Previous studies promoted “faulty gold standards”—results skewed by inclusion of (+)UC caused by “contaminants or asymptomatic bacteriuria” Problem with Schroeder, 2016
Definition of pyuria: >3 WBC/ high power field Definition of (+) leukocyte esterase: “Any” ( trace–(1+)-(2+)-(3+) ) 2011 AAP guidelines
Diagnosis of UTI based on pyuria and significant colony count in and “appropriately collected” urine specimen Lowered threshold for (+)UC: 50,000 colonies of a recognized uropathogen Pyuria definition: >5-10 WBC Questions remain
What is the actual threshold for WBC in UA? Cf: CSF, joint fluid Questions remain
How reproducible is the UA? Technique may effect the UA (semi quantitative) Suggestion of “enhanced UA”: UA by hemocytometer Questions remain
Correlation with acute phase reactants: CRP, pro calcitonin Expect inflammatory markers should reflect invasive disease. Compare UA results and acute phase reactants
Use of DMSA scans to differentiate pyelonephritis vs asymptomatic bacteriuria What Schroeder, 2016 demonstrated
A significant number of WBCs is usually present in bacteremic UTI/urosepsis Noninflammatory bladder colonization (asymptomatic bacteriuria) exists in infants Parting thoughts
Asymptomatic bacteriuria has been recognized since the 1970s Treatment complicated the situation RX temporary clearing recolonization, often with pathogens kidney damage J. Roberts, Peds 135, June, 2015,1126-1127 “The diagnosis of UTI: Liquid Gold and the Problem of a Gold Standards” 1956: >100,000 bact designated arbitrarily as dividing line, UTI vs colonization 1956–66: Adoption of 100,000 bacteria as gold standard; UA overlooked 1970s: Asymptomatic bacteriuria acknowledged; no morbidity Treatment recognized as harmful 1999: Adjust culture threshold: > 50,000; adopted in 2011 AAP guideline 2016: What should be the threshold for WBC and LE in the UA? 2016: 10,000–50,000 significant with (+) UA (depending on organism?) references
“association between uropathogen and pyuria” Shaikh, Peds 2016, p.1-5: (+)UC less likely to exhibit pyuria with enterococcus, Klebsiella, Pseudomonas need better biomarkers than WBC or LE to diagnose UTI
“Reliability of UA for predicting UTI in young febrile children” Bachur, Arch Ped Adol Med 2001,p.60-65: UA sensitivity 82%; UA specificity 92% (WBC>5; LE 1+) T>38.5; M<1yo, F <2yo prevalence UTI 3.3% (Shaw); 2.1% (Bachur) T>39: increased prevalence: F 5%; M 2.2% ( no data circ vs uncirc) references
“screening for UTI in infants in the ER” Shaw, Peds 1998, p.1-5: Enhanced UA (UA + gm stain) most sensitive, but 16% false positive. (+) UA: 2+ LE or (+) nitrite
“Dipstick screen for UTI in febrile infants” Glissmeyer, Peds, 2014, p.1121-27: Dipstick compared favorably with microscopy, sating time and money
“Enhanced UA screening for UTI in ED” Shah, Peds ID 2014, p. 272–5: use of enhanced UA (hemocytometer + G-stain): Automated Uacomparable with manual UA for WBC; Gram stain superior for bacteria