Near-patient testing for infection using urinalysis and immuno-chromatography strips.
Urinary tract infections require costly confirmatory tests such as a urine culture to establish the diagnosis. Elimination of the culture step would save resources; diagnosis and treatment could begin in hours rather than days. We tested a new dip-and-read strip that uses immuno-chromatography (IC) to detect infectious agents in urine. We used a goat-derived polyclonal antibody with reactivity to the cell-wall proteins of Escherichia coli (E. coli). Fluorescein linked to the anti-E. coli antibody served to trap the bacteria on a strip coated with an anti-fluorescein mouse antibody. Blue latex particles were linked to anti-E. coli antibodies by standard methods and were used for detection of E. coli. We found that the combination of leukocyte esterase and nitrite dipsticks gave negative predictive values of 93% for culture-negative urines, i.e., there were very few false-negative results. Using the same dipsticks on culture-positive specimens, the positive predictive values were unacceptably low; we obtained too many false-positive values. By contrast, the IC strips gave negative predictive values of 89%. The major advantage of the IC strips is that the positive predictive values were higher, i.e., there were fewer false-positive results. The combined use of both IC strips and urinalysis dipsticks offers the best strategy for diagnosing infection with dipsticks. The IC strip test could reduce the necessity of a urine culture in patients with suspected infections and provide rapid point-of-care testing.
Pugia
Michael J
MJ
Near Patient Testing Segment, Diagnostic Business Group, Bayer Healthcare, Elkhart, Indiana, USA.
Sommer
Ronald G
RG
Kuo
Hai-Hang
HH
Corey
Paul F
PF
Gopual
Darryl L
DL
Lott
John A
JA
D000919:Antibody-Coated Bacteria Test, Urinary / Q000379:methods* / Q000706:statistics & numerical data; D001437:Bacteriuria / Q000382:microbiology; D002265:Carboxylic Ester Hydrolases / Q000652:urine; D019963:Clinical Chemistry Tests / Q000379:methods / Q000706:statistics & numerical data; D003950:Diagnostic Techniques, Urological / Q000706:statistics & numerical data; D003955:Diagnostic Tests, Routine / Q000379:methods / Q000706:statistics & numerical data; D004906:Erythrocyte Count; D004926:Escherichia coli / Q000276:immunology; D005188:False Negative Reactions; D005189:False Positive Reactions; D005260:Female; D019793:Fluorescein / Q000737:chemistry; D006090:Gram-Negative Bacteria / Q000302:isolation & purification; D006094:Gram-Positive Bacteria / Q000302:isolation & purification; D006801:Humans; D007118:Immunoassay / Q000379:methods / Q000706:statistics & numerical data; D007958:Leukocyte Count; D008297:Male; D008863:Microspheres; D009573:Nitrites / Q000652:urine; D011237:Predictive Value of Tests; D011934:Reagent Strips / Q000737:chemistry; D012016:Reference Values; D016482:Urinalysis / Q000706:statistics & numerical data*; D014552:Urinary Tract Infections / Q000175:diagnosis*; D014556:Urine / Q000737:chemistry / Q000166:cytology / Q000382:microbiology
D009573:Nitrites; D011934:Reagent Strips; C021443:leukocyte esterase; D002265:Carboxylic Ester Hydrolases; D019793:Fluorescein