vitamin d screening recommendations USPSTF

the US Preventive Services Task Force just published their recommendation for vitamin D screening: "the current evidence is insufficient to assess the balance of benefits and harms of screening for vitamin D deficiency in asymptomatic adults", which applies to community-dwelling, nonpregnant adults aged >18 yo seen in a primary care setting and without either signs/symptoms of vitamin D deficiency or conditions where vitamin D treatment is recommended (for review of recommendations, see vit d uspstf recs 2014 in dropbox, or  or go to URL: http://annals.org/article.aspx?articleid=1938935 ; for full systematic review, see vit d uspstf systematic review 2014 in dropbox or either http://annals.org/article.aspx?articleid=1938934  or http://www.uspreventiveservicestaskforce.org/Page/Document/EvidenceReportFinal/vitamin-d-deficiency-screening​ ). this recommendation is largely based on the fact that no study has directly evaluated clinical outcomes or harms comparing those screened for vitamin D deficiency or not. they note:

--there is no consensus about what the cutoff is for vitamin D deficiency. some use <50 nmol/L (<20 ng/mL), others <75 nmol/L (<30 ng/mL), though they do note that some studies do show low levels are associated with increased risk for fractures, functional limitations, cancer (colorectal and others), diabetes, cardiovascular disease, cognitive decline, depression and death.

--there is no standard test used and there are some variations in results depending on the test done. one issue, for example, is that although African-Americans have lower 25(OH)D levels, they also have lower levels of vitamin D binding protein, therefore similar levels of bioavailable vitamin D)

--data are lacking that there is clear benefit for screening of the general community-dwelling population.  current studies have found that there is no benefit in finding/treating vitamin D deficiency on 

cancer, diabetes, risk of death, risk of fractures in those not at high risk of fractures. Data are inadequate about other outcomes, such as psychosocial and physical functioning. also, they did not find any studies on cardiovascular or immune diseases that met their inclusion criteria. they do note that there are some data that treatment of asymptomatic patients is adequate for a few limited outcomes. "vitamin D treatment, with or without calcium, may be associated with decreased risk for mortality and falls in older or institutionalized adults".

--harms: evidence is pretty consistent that the harms of vitamin D supplementation are "small to none", with no studies overall finding an increase in adverse events, hypercalcemia, kidney stones, or GI symptoms

--these recommendations only address screening for the general population, not those specific populations at high risk of falls, fractures, cardiovascular disease, or cancer without first determining 25(OH)-vitamin D levels.

a few points:

--this recommendation only addresses screening for vitamin D deficiency, not the need to have adequate vitamin D levels.

--this recommendation addresses only the general asymptomatic population, not those who are symptomatic or at high risk of vitamin D deficiency, and calls for "more research to determine vitamin D treatment effects in younger noninstitutionalized adults and to clarify the subpopulations that are most likely to benefit from treatment".

--for example, these results may not apply to other populations: vitamin D treatment is associated with decreased risk of death (pooled RR 0.83, with CI 0.70-0.00) in older, institutionalized people, and is associated with lower rate of falls in institutionalized people

--there is pretty clear consensus that vitamin D is an important component of health, with the Institute of Medicine suggesting that adults aged 18-70 yo should take 600 IU of vitamin D and those >70yo should have 800 IU, and that this amount should be sufficient for 97.5% of the population. The US Endocrine Society clinical practice guideline on vitamin D deficiency (see vit d Endocrine Guidelines 2011 in the dropbox, or doi: 10.1210/jc.2011-0385​) also suggested that vitamin D deficiency is remarkably common, and that the primary approach should be generalized supplementation, with testing for vitamin D deficiency in those at risk for deficiency and treating those deficient (<20 ng/mL). they recommend the same intake as the IOM, but comment that these levels may not be enough to raise 25(OH)D levels to 30 ng/mL and may not provide all of the nonskeletal health benefits (which are unproven).

--and i do think there is concern about the correct test to do -- eg, the African-Americans who have low 25(OH)D​ but normal vitamin D binding protein levels, or that obese patients may have higher adipose tissue stores which may be bioavailable.

so, what does this all mean? mostly that there is not enough evidence to screen the general population. it is pretty clear that vitamin D is important, and unlike other vitamins/minerals, is not naturally occurring in many foods, but is generated by UV light exposure. so, unlike other vitamins, where i tend to rant about eating healthfully instead of trying to supplement an individual ingredient here or there, vitamin D levels are an accident of one's latitude. and there are vitamin D receptors throughout the body, including the immune system, with at least one article finding that those patients randomized to vitamin D supplementation who had active pulmonary tuberculosis had accelerated sputum conversion and improvement of several markers of TB-associated inflammatory responses (see vit d and tb treatment pnas 2012 in dropbox, or go to URL: www.pnas.org/cgi/doi/10.1073/pnas.1200072109​ )​. so, perhaps it is correct that we should not be spending the money to check 25(OH)D levels in everyone and that we should just strongly recommend adherence to the supplementation guidelines of the Institute of Medicine --  with the only caveat being that there may be better adherence with vitamin D supplementation if the patient knows that they themselves are vitamin D deficient instead of just being told to drink more milk/orange juice/take supplements as one of many health different provider suggestions.