Screening for urinary tract infection with the Sysmex UF-1000i urine flow cytometer.
The diagnosis of urinary tract infection (UTI) by urine culture is time-consuming and can produce up to 60 to 80% negative results. Fast screening methods that can reduce the necessity for urine cultures will have a large impact on overall turnaround time and laboratory economics. We have evaluated the detection of bacteria and leukocytes by a new urine analyzer, the UF-1000i, to identify negative urine samples that can be excluded from urine culture. In total, 1,577 urine samples were analyzed and compared to urine culture. Urine culture showed growth of ≥10(3) CFU/ml in 939 samples (60%). Receiver operating characteristics (ROC) curves and ROC decision plots were been prepared at three different gold standard definitions of a negative urine culture: no growth, growth of bacteria at <10(4) CFU/ml, and growth of bacteria at <10(5) CFU/ml. Also, the reduction in urine cultures and the percentage of false negatives were calculated. At the most stringent gold standard definition of no growth, a chosen sensitivity of 95% resulted in a cutoff value of 26 bacteria/μl, a specificity of 43% and a reduction in urine cultures of only 20%, of which 14% were false negatives. However, at a gold standard definition of <10(5) CFU/ml and a sensitivity of 95%, the UF-1000i cutoff value was 230 bacteria/μl, the specificity was 80%, and the reduction in urine cultures was 52%, of which 0.3% were false negatives. The applicability of the UF-1000i to screen for negative urine samples strongly depends on population characteristics and the definition of a negative urine culture. In our setting, however, the low workload savings and the high percentage of false-negative results do not warrant the UF-1000i to be used as a screening analyzer.
Máxima Medical Centre, Clinical Laboratory, De Run 4600, 5504 DB Veldhoven, The Netherlands. mac_broeren@yahoo.com
Maarten A C
MA
Broeren
Semiha
S
Bahçeci
Huib L
HL
Vader
Niek L A
NL
Arents
D001419:Bacteria / Q000302:isolation & purification; D001424:Bacterial Infections / Q000175:diagnosis*; D019411:Clinical Laboratory Techniques / Q000379:methods*; D005260:Female; D005434:Flow Cytometry / Q000379:methods*; D006801:Humans; D007962:Leukocytes; D008297:Male; D008403:Mass Screening / Q000379:methods*; D012680:Sensitivity and Specificity; D014552:Urinary Tract Infections / Q000175:diagnosis*; D014556:Urine / Q000166:cytology* / Q000382:microbiology*
Clin Chem Lab Med. 1998 Dec;36(12):909-17
9915222
N Engl J Med. 1993 Oct 28;329(18):1328-34
8413414
J Clin Microbiol. 2001 Nov;39(11):4169-71
11682551
Clin Chim Acta. 2000 Nov;301(1-2):1-18
11020458
J Clin Pathol. 2006 Jun;59(6):661-2
16731608
Am J Med. 2002 Jul 8;113 Suppl 1A:5S-13S
12113866
Int Urol Nephrol. 2002;34(2):175-8
12775087
Clin Nephrol. 2001 May;55(5):384-92
11393384
Lancet Infect Dis. 2010 Apr;10(4):240-50
20334847
Am J Clin Pathol. 2007 Dec;128(6):922-5
18024316
Diagn Microbiol Infect Dis. 2009 Oct;65(2):103-7
19748419
Clin Chem Lab Med. 2010 Aug;48(8):1107-11
20482296
Clin Chim Acta. 2008 Jun;392(1-2):30-3
18348868
N Engl J Med. 2010 May 13;362(19):1804-13
20463340
J Clin Microbiol. 2000 Aug;38(8):2870-2
10921941
Clin Chim Acta. 2010 Aug 5;411(15-16):1137-42
20359474
Am J Clin Pathol. 2010 Apr;133(4):577-82
20231611
Clin Microbiol Infect. 2002 Oct;8(10):662-8
12390285
Clin Chem Lab Med. 2007;45(9):1251-6
17635081
Clin Chem Lab Med. 2010 Feb;48(2):289-92
19961394
JAMA. 2002 May 22-29;287(20):2701-10
12020306
BMC Urol. 2004 Jun 02;4:4
15175113