Ann Lab Med.  2013 May;33(3):190-192. 10.3343/alm.2013.33.3.190.

Analysis of the Stability of Urea in Dried Blood Spots Collected and Stored on Filter Paper

• Quraishi R
• Lakshmy R
• Mukhopadhyay AK
• Jailkhani

• KMID: 1781324
• DOI: http://doi.org/10.3343/alm.2013.33.3.190

Abstract

The ability to use dry blood spots (DBSs) on filter paper for the analysis of urea levels could be an important diagnostic tool for areas that have limited access to laboratory facilities. We developed a method for the extraction and quantification of urea from DBSs that were stored on 3M Whatman filter paper and investigated the effect of long-term storage on the level of urea in DBSs. DBSs of 4.5 mm in diameter were used for our assay, and we determined the urea levels in blood using a commercially available enzymatic kit (UV GLDH-method; Randox laboratories Ltd., UK). The DBSs on filter discs were stored at 4degrees C or at 37degrees C for 120 days. The mean intra- and inter-assay coefficient of variance for our method of urea extraction from dried blood was 4.2% and 6.3%, respectively. We collected 75 fresh blood samples and compared the urea content of each fresh sample with the urea content of DBSs taken from corresponding fresh blood samples. Regression analysis reported a regression coefficient (r) value of 0.97 and a recovery of urea from dried spots was 102.2%. Urea concentrations in DBSs were stable for up to 120 and 90 days when stored at 4degrees C and 37degrees C, respectively. Our results show that urea can be stored and quantitatively recovered from small volumes of blood that was collected on filter paper.

Keyword

Urea; Filter Paper; Dried blood spot; Stability

MeSH Terms

*Dried Blood Spot Testing
Filtration
Humans
Paper
Regression Analysis
Temperature
Urea/*blood
Urea

Figure

• 

  Fig. 1 Effect of storage of dried blood on urea levels. The figure represents mean (+/-SD) blood urea levels measured after storage of filter disc for 15, 30, 60 and 90 days at 37℃ and at 4℃ (N=20). The values obtained at different time periods were compared by within-subject ANOVA (F=1.56, P=0.25 at 37℃ and F=1.60, P=0.24 at 4℃).

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