Thank you Michael for your opinion.

Low serum vit-D has been known to be a predictor of cardiovascular risk including ischemic stroke (http://www.ncbi.nlm.nih.gov/pubmed/26184826). Diabetes, hypertension and stroke are increasing in my setting which we believe might be due to deficient serum 25(OH)D, or we might be wrong, and without confirming this how can we blindly tell people to eat decent nutrition and supplementary D just because you have cardiovascular disease. Therefore, being a researcher from poor country I had put the above question. I would highly appreciate if you know a cheaper and reliable technique to measure serum 25(OH)D.

You last paragraph was interesting but if you shift the paradigm the scientist you have mentioned, might want to measure the temperature of a burning house to prevent/stop other houses and homes from burning down.

Thanks Michael. We did conduct a study in 2013 using a cheaper method which according to papers is less reliable/precise (obviously than HPLC), where we found our study population of ischemic stroke had deficiency vitamin D level (https://www.researchgate.net/publication/287210695_Status_of_Vitamin_D_and_its_Association_with_Stroke_Risk_Factors_in_Patients_with_Acute_Ischemic_Stroke_in_a_Tertiary_Care_Hospital). Recently we also have planned to conduct what you have suggested, but then we want to record the 25(OH)D with much reliable method (excellent if cheaper too) together with providing supplements in a same study. I'm sure your expertise would help us with few suggestions. Thanks again

Article Status of Vitamin D and its Association with Stroke Risk Fac...

The cost of vitamin D testing is between $40 and $70 per sample http://www.vitamindwiki.com/Low+cost+vitamin+D+Blood+Tests

The cost of an HPLC is $50,000 to $60,000 up front plus up to $40,000 per year in supplies (120 samples per day) 24 hours per day 7 days a week. You also have to add in the cost for 3 to 4 full time employees to prepare the samples, run and maintain the instrument, review the data, and send out the results. For LC-MS the up front cost is much higher $400,000 to $500,000 for the instrument then up to $90,000 per year in supplies, again include salaries and overhead for 3 to 4 full time personnel. I included a yearly service contract which typically is 10% of the initial cost of the instrument per year in the supplies budget.

Metabolon and Bionall provide contract analysis services for vitamin D and metabolites.

Thanks Prof Levision and Dr Chen.

HPLC and LC-MS/MS are 5 to 10 times more expensive than ordinary immuno-assays.

I suggest hire a small analyser like Fuji-Rebio has and use a kit that has a long shelf-life and fair prize. Serum samples, after centrifugation can be stored in the freezer for months if needed.