Hi everyone, I want to understand explicitly the rationale behind working on a small sample size in the field of virology. I have read several publications whereby just a couple viruses were utilized in conducting experiments without taking into consideration, I presume, of the importance of power and effect size in determining an appropriate sample size required for the study. I am presently working on a grant proposal so I decided to throw this question out to an open space to seek clarification on this important aspect of conducting a valid and acceptable scientific research. I welcome everyone’s contributions. Thank you
Hi Fatai,
in general, it comes down to standardization. If you want to answer a specific question, for example how an antiviral compound may act, you want to minimize unnecessary variation. The less variables you have, the more precise you may be able to answer the question. This also takes into account, that there are many virus out there that do not differ much between separate isolates/strains. However, for some viruses or problems your question is totally justified, e.g. HIV/SIV or Influenza. In these cases, you still want to get a first insight how something may work by testing it on a single isolate/strain. Then, if you discovered something that may be worth to be further followed, you have to extend your observations to a more realistic setting.
I hope, this helped.
Very often it is not easy to quantify viruses in a standardized manner. Many groups buy them from companies and therefore have not ressources to pay a hogh amount of money. It is much easier to run sensitive methods or cultures and spare on viral material, which is standardized.
Thank you Christian.
@Denis I actually meant number of virus strains or isolates included in studies and not the virus titer.
@Fatai, usually the laboratory have some viruses "in use" - they are well characterized and generation, purification and titration are routine procedures. Actually that number is small - it is very difficult and expensive to have a lot of viruses/strains in use. Typically a lot of viruses are in collection, but just several strains are at work.
Generally, it is not necessary to have a lot of different viruses for a study. For example, if we do a screening for antiviral activity for several compounds, it is enough to have just several different viruses from important families, e.g. Herpesviridae, Orthomyxoviridae, Poxviridae and Flaviviridae. Typically, 3-5 viruses.
Good luck!
Hi Fatai,
in general, it comes down to standardization. If you want to answer a specific question, for example how an antiviral compound may act, you want to minimize unnecessary variation. The less variables you have, the more precise you may be able to answer the question. This also takes into account, that there are many virus out there that do not differ much between separate isolates/strains. However, for some viruses or problems your question is totally justified, e.g. HIV/SIV or Influenza. In these cases, you still want to get a first insight how something may work by testing it on a single isolate/strain. Then, if you discovered something that may be worth to be further followed, you have to extend your observations to a more realistic setting.
I hope, this helped.
I guess you wouldn't use different strains of a given virus, unless it is not a conserved virus. For examples, people studying MERS-CoV used EMC/2012 isolate since it's available in a number of labs and it does not differ, very much, from other strains in terms of genetic make-up.
It depends on the your question/hypothesis. If you are working on virus replication, you can use viruses belonging to the same family to prove that they behave similarly or differently.
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