Study On The Diagnostic Value Of Urine Dry Chemical Testing And Flow Cytometry Analysis For Urinary Tract Infection

Objective:To investigate 899 patients with suspected Urinary tract infection(UTI)in Wuxi from 2014 to 2016 retrospectively,and evaluate the diagnostic value of urine dry chemical testing and urine flow cytometry analysis for UTI.Materials and Methods:1.Source of data:889 urine samples from the patients with suspected UTI in Wuxi Ninth People's Hospital affiliated to Soochow University from June2014 to July 2016 were analyzed retrospectively.2.Urine dry chemical analysis:Roche COBAS u 411 semi-automatic urine dry chemistry analyzer was used to detect leukocyte esterase(LE),nitrite(NIT)and protein(PRO).3.Urine flow cytometry analysis:UF1000i flow cytometer was used to analyze leukocyte(LEU),bacteria count(BACT)and bacterial morphology.According to reference,the angle of the scatter cloud with the x-axis determines if the bacteria found were classified as rods(<30~°)or cocci/mixed(>30~°).4.Statistical analysis:SPSS17.0 software was used for general statistical analysis.The receiver operating characteristic(ROC)curve was used to determine the best cutoff values of BACT and LEU.The urine culture was used as the gold standard for UTI.Sensitivity(SEN),specificity(SPE),accuracy(ACC),positive predictive value(PPV),negative predictive value(NPV),positive likelihood ratio(+LR),negative likelihood ratio(-LR),Youden index(YI)and the rate of misdiagnosis as well as the missed diagnosis were tested.The situation of bacteria scatter diagram was compared with the urine culture of the corresponding specimen.Mann-Whitney U was used to compare the differences of LEU and BACT between the positive and negative specimens of urine cultures.The cutoff value of BACT and LEU in different gender were compared using chi-square test.P<0.05 indicates statistical difference,P<0.01indicates significant statistical difference.Results:1.The overall infection status245 of the 899 urine specimens were positive,the infection rate was about27.6%.Among the 245 positive specimens,44 were infected by Gram-positive bacteria(18%)and 201 were infected by Gram-negative bacteria(82%).There were 105 specimens infected by Escherichia coli in Gram-negative bacteria(52.2%).2.Urine dry chemical testingThe single and combined indexes evaluation suggested that NIT was more significant for the diagnosis of UTI(SPE,96.7%;ACC,85.2%;PPV,86.5%;+LR,1677.3%;YI,51.4%;the rate of missed diagnosis,3.3%).3.The best cutoff value of BACT and LEU of UF1000i urine flow cytometerThe best cutoff value of BACT in the total population,male and female was119/?l,118/?l and 583/?l,respectively;the best cutoff value of LEU in the population,male and female was 81.5/?l,91/?l and 137.5/?l,respectively.There was significant difference of the cutoff value of BACT and LEU in female urine specimens(P<0.01).4.Urine flow cytometer analysisThe single and combined indexed evaluation suggested that BACT was more significant for the diagnosis of UTI(SEN,95.5%;SPE,88.7%;ACC,90.6%;NPV,98.1%;-LR,5.0%;YI,84.2%;the rate of missed diagnosis,4.5%).5.The combination of urine dry chemical testing and urine flow cytometry analysisThe SEN of the combination of urine dry chemical testing and urine flow cytometry analysis was low,but the SPE was high(SEN,27.8%;SPE,98.8%;ACC,79.2%;PPV,89.5%;+LR,2234.3%;the rate of missed diagnosis,1.2%).6.The comparison of the results of flow cytometer UF1000i with the results of urine culturesBACT in positive and negative urine cultures was 8616(2285~21424)/?l and 10(3~32)/?l,respectively.There was significant difference(Z=-21.8,P<0.01);the count of LEU in positive and negative urine cultures was 318(95.5~1127.5)/?l and 18(5~75.8)/?l,respectively.There was significant difference(Z=-15.2,P<0.01).7.UF1000i scatter diagram analysis of the positive urine culturesOf the 201 positive cultures that detected Gram-negative rods,167 were classified as rods,24 were classified as cocci using UF1000i flow cytometry analysis.And the rest 10 specimens didn't form an angle in UF1000i scatter diagram.The coincidence of UF1000i flow cytometer and urine cultures was82%.Of the 44 positive cultures that detected Gram-positive cocci,30 were classified as cocci,12 were classified as rods using UF1000i flow cytometry analysis.And the rest 2 specimens didn't form an angle in UF1000i scatter diagram.The coincidence of UF1000i flow cytometer and urine cultures was68%.Conclusions:1.The performance of NIT of dry chemical testing for UTI diagnosis was better.2.Female cutoff value of BACT and LEU in UF1000i flow cytometry analysis was much higher than cutoff value of male,which suggested that different cutoff value should be designed for various gender detection in clinic.3.The diagnostics of UF1000i urine flow cytometer is satisfied.BACT detected by UF1000i could be used for screening patients of UTI prior to urine cultures.4.The pathogenic bacterial morphology could be distinguished preliminary through the scatter diagram of urine flow cytometer,which is useful for antibiotics selection in clinic.