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Post-collection, pre-measurement variables affecting VEGF levels in urine biospecimens.

Hayward RM, Kirk MJ, Sproull M, Scott T, Smith S, Cooley-Zgela T, Crouse NS, Citrin DE, Camphausen K - J. Cell. Mol. Med. (2008 Jan-Feb)

Bottom Line: The results of this study indicate that time to freeze up to 4 hrs, number of freeze-thaw cycles between one and five, and different types of polypropylene tubes did not have statistically significant effects on measured urinary VEGF levels.Urinary sediment had higher VEGF levels than supernatant in five of six samples from healthy patients.It is not clear whether there is an active agent in the sediment causing this increase or if the sediment particles themselves are affecting the accuracy of the assay.Therefore, we recommend centrifuging urine, isolating the supernatant, and freezing the sample in polypropylene microcentrifuge tubes or cryogenic vials within 4 hrs of collection.In addition, we recommend the use of samples within five freeze-thaw cycles.

View Article: PubMed Central - PubMed

Affiliation: Radiation Oncology Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Department of Health and Human Services, Bethesda, MD 20892-1002, USA.

ABSTRACT
Angiogenesis, the development and recruitment of new blood vessels, plays an important role in tumour growth and metastasis. Vascular endothelial growth factor (VEGF) is an important stimulator of angiogenesis. Circulating and urinary VEGF levels have been suggested as clinically useful predictors of tumour behaviour, and investigations into these associations are ongoing. Despite recent interest in measuring VEGF levels in patients, little is known about the factors that influence VEGF levels in biospecimens. To begin to address this question, urine samples were collected from patients with solid tumours undergoing radiotherapy and healthy volunteers. Four factors were examined for their effects on VEGF concentrations as measured by chemiluminescent immunoassay: time from sample collection to freezing, number of specimen freeze-thaw cycles, specimen storage tube type and the inclusion or exclusion of urinary sediment. The results of this study indicate that time to freeze up to 4 hrs, number of freeze-thaw cycles between one and five, and different types of polypropylene tubes did not have statistically significant effects on measured urinary VEGF levels. Urinary sediment had higher VEGF levels than supernatant in five of six samples from healthy patients. It is not clear whether there is an active agent in the sediment causing this increase or if the sediment particles themselves are affecting the accuracy of the assay.Therefore, we recommend centrifuging urine, isolating the supernatant, and freezing the sample in polypropylene microcentrifuge tubes or cryogenic vials within 4 hrs of collection.In addition, we recommend the use of samples within five freeze-thaw cycles.

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Related in: MedlinePlus

Effect of freeze-delay time on urinary VEGF concentrations for nine cancer patients. Values presented are means ±SEM (n= 3).
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fig01: Effect of freeze-delay time on urinary VEGF concentrations for nine cancer patients. Values presented are means ±SEM (n= 3).

Mentions: In each of the nine samples, there was no significant difference between urinary VEGF levels in samples frozen at 0, 1 and 4 hrs post-collection at the 95% confidence level (Fig. 1, unpaired t-tests, two-tailed with unequal variances; Table 1, paired t-tests, two-tailed).There was a non-statistically significant trend toward increased urinary VEGF levels in samples left at room temperature for 24 hrs before freezing (P= 0.16, paired two-tailed t-test), as seven of the nine samples tested showed elevated VEGF concentrations.


Post-collection, pre-measurement variables affecting VEGF levels in urine biospecimens.

Hayward RM, Kirk MJ, Sproull M, Scott T, Smith S, Cooley-Zgela T, Crouse NS, Citrin DE, Camphausen K - J. Cell. Mol. Med. (2008 Jan-Feb)

Effect of freeze-delay time on urinary VEGF concentrations for nine cancer patients. Values presented are means ±SEM (n= 3).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2367114&req=5

fig01: Effect of freeze-delay time on urinary VEGF concentrations for nine cancer patients. Values presented are means ±SEM (n= 3).
Mentions: In each of the nine samples, there was no significant difference between urinary VEGF levels in samples frozen at 0, 1 and 4 hrs post-collection at the 95% confidence level (Fig. 1, unpaired t-tests, two-tailed with unequal variances; Table 1, paired t-tests, two-tailed).There was a non-statistically significant trend toward increased urinary VEGF levels in samples left at room temperature for 24 hrs before freezing (P= 0.16, paired two-tailed t-test), as seven of the nine samples tested showed elevated VEGF concentrations.

Bottom Line: The results of this study indicate that time to freeze up to 4 hrs, number of freeze-thaw cycles between one and five, and different types of polypropylene tubes did not have statistically significant effects on measured urinary VEGF levels.Urinary sediment had higher VEGF levels than supernatant in five of six samples from healthy patients.It is not clear whether there is an active agent in the sediment causing this increase or if the sediment particles themselves are affecting the accuracy of the assay.Therefore, we recommend centrifuging urine, isolating the supernatant, and freezing the sample in polypropylene microcentrifuge tubes or cryogenic vials within 4 hrs of collection.In addition, we recommend the use of samples within five freeze-thaw cycles.

View Article: PubMed Central - PubMed

Affiliation: Radiation Oncology Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Department of Health and Human Services, Bethesda, MD 20892-1002, USA.

ABSTRACT
Angiogenesis, the development and recruitment of new blood vessels, plays an important role in tumour growth and metastasis. Vascular endothelial growth factor (VEGF) is an important stimulator of angiogenesis. Circulating and urinary VEGF levels have been suggested as clinically useful predictors of tumour behaviour, and investigations into these associations are ongoing. Despite recent interest in measuring VEGF levels in patients, little is known about the factors that influence VEGF levels in biospecimens. To begin to address this question, urine samples were collected from patients with solid tumours undergoing radiotherapy and healthy volunteers. Four factors were examined for their effects on VEGF concentrations as measured by chemiluminescent immunoassay: time from sample collection to freezing, number of specimen freeze-thaw cycles, specimen storage tube type and the inclusion or exclusion of urinary sediment. The results of this study indicate that time to freeze up to 4 hrs, number of freeze-thaw cycles between one and five, and different types of polypropylene tubes did not have statistically significant effects on measured urinary VEGF levels. Urinary sediment had higher VEGF levels than supernatant in five of six samples from healthy patients. It is not clear whether there is an active agent in the sediment causing this increase or if the sediment particles themselves are affecting the accuracy of the assay.Therefore, we recommend centrifuging urine, isolating the supernatant, and freezing the sample in polypropylene microcentrifuge tubes or cryogenic vials within 4 hrs of collection.In addition, we recommend the use of samples within five freeze-thaw cycles.

Show MeSH
Related in: MedlinePlus