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Clinical Chemistry 46: 1384-1386, 2000;
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(Clinical Chemistry. 2000;46:1384-1386.)
© 2000 American Association for Clinical Chemistry, Inc.

Articles

Stability of Common Analytes in Urine Refrigerated for 24 h before Automated Analysis by Test Strips

Paul Frooma,1, Barbara Bieganiec1, Zahava Ehrenrich1 and Mira Barak1

1 Central Laboratory of Haifa and Western Galilee, Clalit Health Services, Nesher, Israel.
a Address correspondence to this author at: Central Laboratory of Haifa and Western Galilee, Clalit Health Services, Nesher, Israel. Fax 972-4-8209094; e-mail paulf{at}ioh.org.il

Background: Central outpatient laboratories might find processing large numbers of urinary samples that arrive in the late afternoon inconvenient and refrigerate them overnight before testing. Furthermore, in certain settings clinics might have difficulty assuring that the urine arrives at the laboratory during the same day as the collection. Because the stability of urine samples for delayed automated dipstick analysis (Supertron) is unknown, after defining precision, we retested urines refrigerated for 24 h to determine stability.

Methods: Urinalysis was done twice on the same day and repeated after the sample was refrigerated for 24 h. Combur-10S (Roche Diagnostics) dipsticks were read automatically by a Supertron analyzer. Repeat tests on the same day were compared with tests after storage.

Results: Leukocyte esterase had high precision, but after storage ~25% of the positive samples were less reactive (P <0.005). Precision of hemoglobin retests was also high but declined significantly after storage for 24 h. Urine protein values increased after storage. The precision and stability were excellent for nitrites, glucose, and ketones.

Conclusions: The stability of the automated dipstick urinalysis varies with the substance tested. After refrigeration for 24 h, there is a risk of false-positive results for protein, false-negative results for leukocytes and erythrocytes, and little effect on glucose, nitrite, and ketone values.




The following articles in journals at HighWire Press have cited this article:


Home page
 Clin. Chem.Home page
P. Froom, R. Etzion, and M. Barak
What Is an Abnormal Test Strip Urinary Erythrocyte Concentration?
Clin. Chem., March 1, 2004; 50(3): 673 - 675.
[Full Text] [PDF]

Home page
 Clin. Chem.Home page
J. Penders, T. Fiers, and J. R. Delanghe
Quantitative Evaluation of Urinalysis Test Strips
Clin. Chem., December 1, 2002; 48(12): 2236 - 2241.
[Abstract] [Full Text] [PDF]


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