Since the authors recommend the use of these proposed decision limits, that implies that some decision must be made by the doctor if the results are outside of those ranges. That decision seems fairly straightforward although the authors do not suggest any interventions. For low levels of sodium and potassium, supplements are available to boost serum levels in the form of table salt for sodium and supplements for potassium. Recent studies indicate that many people are deficient in minerals (2). For levels that are too high, the first intervention should be checking people for hydration levels, because many people, particularly the elderly, are chronically dehydrated(3). A more drastic intervention for high K levels might be diuretic therapy, although assessment for hypertension would be required and there is a prominent risk of low K (hypokalemia) levels developing as a side-effect of diuretic therapy. In addition, a recent study has shown an increased risk of mortality in patients with high Na excretion in the urine occurs only for patients who are hypertensive (4). I summarize this data in tabular form in Table 2.
The same group performed a similar study for K excretion in the urine (5) and showed the very interesting result that increased K excretion in the urine is actually associated with a lower death rate, as shown in the Table 3 below.
1. Solinger AB, Rothman SI. Risks of mortality associated with common laboratory tests: a novel, simple and meaningful way to set decision limits from data available in the electronic medical record. Clin Chem Lab Med DOI 10.1515/cclm-2013-0167.
2. Blumberg JB et al. Vitamin and mineral intake is inadequate for most Americans: What should we advise patients about supplements? Int Med News Supp Sept 2016, 51-58.
3. Hooper L et al. Diagnostic accuracy of calculated serum osmolarity to predict dehydration in older people: Adding value to pathology lab reports. BMJ Open October 2015 DOI: 10.1136/bmjopen- 2015-008846
4. Mente A et al. Associations of urinary sodium excretion with cardiovascular events in individuals with and without hypertension: a pooled analysis of data from four studies. Lancet 388: 465-475, 2016.
5. O’Donnell M et al. Urinary sodium and potassium excretion, mortality and cardiovascular events. NEJM 371: 612-623, 2014.