Drop Date: September 2018

In This Drop: Rigor and Reproducibility (Part 1): How Good Are Your Lab Results?

Rigor and Reproducibility is a three-part series on the steps researchers can take to improve the quality of their salivary bioscience data.

High Quality Labs: High Quality Results

As researchers, we understand the necessity of minimizing variability from external sources that can negatively impact data interpretation. Variability can arise from many factors, such as differences between samples, participant noncompliance, specimen handling, differences between assay kits, and/or differences between laboratories. Controlling for sources of variability leads to higher data consistency, which is essential in establishing precise results and drawing reliable conclusions from generated data. Part 1 of this 3-part series on rigor and reproducibility in salivary bioscience will take an in-depth look at improving the quality of your salivary bioscience research based on the findings from a 2017 study: “Measurement of cortisol in saliva: a comparison of measurement error within and between international academic-research laboratories,” from Calvi et al.

While it can be difficult to control sample-specific physiological variability and participant noncompliance, researchers can easily control which assays and laboratory are utilized to generate data for their studies.  Dr. Calvi’s team highlighted how researchers can obtain better results by studying the effect of quality laboratories on measurement precision when using the Salimetrics Salivary Cortisol Assay kit. The study design involved sending aliquots of 100 individual samples to nine different qualified labs, and comparing the results generated from these samples by each lab.  The results were impressive; in these high-quality labs, the average intra-assay (same lab, same plate) CV was only 6.2%, and the average inter-assay (same lab, different plate) CV was only 6.36%.  Furthermore, when the results of the labs were compared with each other, over 90% of the variation was attributed to differences in the samples, only 7.93% was attributed to the differences in the labs, and just 1.76% could be attributed to the Salimetrics’ cortisol assay.  Keep in mind that in research, normal acceptance values for inter- and intra-assay CVs are typically less than 15% and 10%, respectively, and both the inter- and intra-assay variation observed in the study were substantially better. The researchers concluded that qualified laboratories contributed to a very small portion of measurement variation. This conclusion is highly relevant – better laboratories combined with better assays will produce better results that are reliable and precise for the scientific community.

Choosing Better Results

Researchers have the power to reduce variability in the salivary bioscience testing phase of their study. The first step is selecting an established, high-quality assay that is routinely published with the lowest CVs, such as the Salimetrics’ salivary cortisol assay.  Next, the researcher should examine and choose an established, high-quality laboratory experienced for the assay being used before they send their samples. Salimetrics provides extensive laboratory quality control which commonly produces CVs of less than 3% for analytes such as salivary cortisol.

The research shows that if these two factors are handled correctly, the remaining source of variation, the samples, can be properly addressed to achieve better results.  Often, sample variation is the product of poor participant compliance, use of non-validated collection methods or poor sample handling.  Salimetrics provides researchers extensive resources and collection methods for identifying and limiting variability in samples.  Part 2 of this 3-part series on rigor and reproducibility in salivary bioscience will take an in-depth look at improving the quality of samples and limiting sample variation.

A Significant Conclusion

To reduce overall variation in research studies, Calvi et al. determined that it is essential to choose a laboratory which meets the current standards for an experienced, qualified laboratory and a high-quality assay, such as the Salimetrics salivary cortisol assay.  By choosing to do so, researchers can easily remove a substantial degree of variability from their research. It can be that simple.