Power to the People

Opinion on direct-to-consumer (DTC) lab tests is divided – while some believe that patients should take charge of their own health in every way, others are rightfully concerned that untrained eyes might misunderstand the meaning, significance or reliability of the results. Regardless of expert opinions on the subject, as medical technology becomes increasingly accessible, it seems that consumer testing is here to stay. But what is it that patients are learning from these tests – and can it be trusted? To find out, a team of researchers from Mount Sinai’s Icahn School of Medicine embarked on a cohort study of healthy adults using popular over-the-counter tests (1).

To examine the performance of these tests, 60 adults were administered 22 common laboratory tests from either a DTC company (Theranos, which uses fingerprick diagnostics) or clinical testing services (Quest and LabCorp, both of which use venipuncture). The tests included a complete blood count panel, leukocyte subsets, lipid panel, inflammation, kidney and liver labs. The blood draws were completed within the span of 6.5 hours; each patient had one venipuncture and one fingerprick early in the day, then another of each draw late in the day.

What did they find? The DTC test returned missing data more often than the clinical services (2.2 percent, as compared with 0.2 and 0 percent) and reported more measures outside the normal range (12.2 percent, as compared with 8.3 and 7.5 percent). Most notably, results for mean corpuscular hemoglobin concentration, lymphocyte count, and cholesterol components were out of range more often than expected, with ratios between the consumer test and the lab services ranging from 1.6 to 4.5. Nonequivalence was also a problem, not just between the low-volume and standard tests, but also between the two clinical testing services – though here, again, the consumer test deviated most. Unexpectedly, inter-subject and inter-service variability had a significant impact on results, even within clinical testing services – a finding that may have implications for end-user interpretations of results, and ultimately for treatment decisions at the point of care.

What does this mean for DTC services? Should they be scrapped? Not necessarily; according to the report’s authors, these kinds of tests cost substantially less than traditional services, and are often more accessible for patients with limited time or mobility. Rather, they suggest that it’s important for test manufacturers and regulatory bodies to gain a greater understanding of the sources of variability, so that results can be interpreted in context and, eventually, testing technologies improved. As consumer testing doesn’t appear to be a transient phenomenon, the goal should be to provide results as accurate and reliable as possible.