Hi,

It is important to first check whether miR-16 is regulated in your samples before using it as a normaliser as there is a good possibility that it could be changing. If this is the case, you results will be affected. A brief look through Google implicates a potential role for miR-16 in cancer, which could affect the levels in serum.

Ideally, you want to look for a few and use something like NormFinder to identify potential miRNA that you can use as a normaliser - this is particularly useful if you have array or sequencing data that you can use to identify one or two that are stable across your samples. You might even want to use more than one miRNA and use a group of three for example and use the average for normalisation.

In short, whether miR-16 is appropriate for your studies depends on whether miR-16 is stably expressed across your samples, or if there are other miRNA that are better suited. Remember, what works for other people may not work best for you.

Hope this helps.

Hi Lobna

You can try with some commercial miRNA like a internal control from other spices, for example add ath-miR-159a in your samples and measure also by PCR. In order to avoid the clinical effect of your samples between patients. 

Remember, in the serum there are lipoproteíns and them carry miRNAs dependent on the fraction (LDL, HDL,..) as miR-223. Perhaps, the lipid profile can influence in your results

Hope this helps