Detection of low-molecular-weight proteins in urine by dipsticks.
BACKGROUND
Testing of urines with dipsticks for proteinuria, glycosuria, etc., is common practice. A deficiency with currently available dipsticks is their lack of chemical sensitivity and underestimation of low-molecular-weight proteins such as light chains.


METHODS
We experimented with a number of dyes that gave an easily recognized color change on dipsticks for various low-molecular-weight proteins such as alpha-1-glycoprotein, alpha-1- and beta-2-microglobulin, and kappa and lambda light chains. We were successful in formulating a dye for impregnating dipsticks that gave a color change with low-molecular-weight proteins.


RESULTS
Most dipsticks will measure proteins down to about 1 g/l. Our composite of two dyes (described here as the "TPR" dipsticks) gave reproducible results for protein concentrations of >/=300 mg/l, and detected low-molecular proteins. The TPR reagent is resistant to interferences from many compounds; also, the protein results are not altered in a given urine at a pH between 5 and 8.


CONCLUSIONS
We have developed a dipstick that detects low-molecular-weight proteins. The dipsticks are easy to use and are suitable for outpatient or point-of-care testing. The precision of the dipsticks is satisfactory and is only marginally lower than quantitative spectrophotometric methods using pyrogallol red (PYR).
Pugia
Michael
M
Diagnostic Business Group, Bayer Corporation, Elkhart, IN, USA.
Newman
David J
DJ
Lott
John A
JA
D'Mello
Lucia
L
Clark
Larry
L
Profitt
James A
JA
Cast
Todd
T
D004396:Coloring Agents; D003404:Creatinine / Q000652:urine; D006801:Humans; D008970:Molecular Weight; D011506:Proteins / Q000032:analysis*; D011507:Proteinuria / Q000175:diagnosis / Q000652:urine*; D011786:Quality Control; D011934:Reagent Strips; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D016482:Urinalysis / Q000379:methods
D004396:Coloring Agents; D011506:Proteins; D011934:Reagent Strips; D003404:Creatinine