Understanding DNA Testing Accuracy and Variability: Why My Ancestry DNA Test Changed
Many individuals are surprised to find that their DNA test results for ancestry can change over time, sometimes drastically. This article explores the nuances of DNA testing, why results may vary, and how to interpret these changes accurately.
Why Are DNA Test Results sometimes Inaccurate?
It is important to acknowledge that DNA test results are not always 100% accurate. One reason for this inaccuracy is the subjective nature of the analysis. As one knowledgeable individual explained on Quora, differences in results of 1 or 2 percent were sometimes fabricated during analysis for humor. According to this individual, such misinterpretations frequently occur in the field.
Another contributing factor is the variability across different DNA testing companies. It is quite common for different companies to provide varying results for the same individual. This variability is due to differences in the quality and quantity of reference data, algorithms used, and the overall database.
Databases and Reference Populations
When you submit a DNA sample, you contribute to the database used by the testing company. This information is then used to estimate your ancestry through comparisons with other samples in the database. Therefore, as more individuals contribute to the database, the accuracy and detail of these estimates improve. However, the initial results can be less precise due to the limited amount of data available at the time of testing.
Understanding Your Test Results Over Time
I have taken four different DNA tests over the last 11 years. These tests provide broad regional information but do not pinpoint specific locales. In my case, the results from these four tests are different but consistent on a regional or continental level. This illustrates the variability in results but also the reliability of the broader ethnic classifications.
For instance, my ethnicity has been consistently classified as Northwestern/central European, but the specific countries identified vary depending on the testing company. Over time, the accuracy of identifying specific regions improves as more data is collected and analyzed. This is evident in the improvements in the ancestry results over the years.
Interpreting Raw Data vs. Analytical Interpretations
Recent advances in DNA testing have made it possible to download raw data directly from many testing platforms, including Comparing the raw data obtained from these tests is essential to understanding the true results. Raw data, which includes the genetic markers and their corresponding traits, does not change over time. It is the interpretation and analysis of this data that can be influenced by various factors, such as updates in the reference population or changes in the mathematical models used.
It is crucial to recognize that the ethnicity analysis is not part of the raw data; it is an interpretation of the data. Therefore, any changes in ethnicity results may not reflect a change in your genetic makeup but rather an improvement in the analytical interpretation. Some companies, like , have made significant improvements in their ethnicity analysis over time, leading to more accurate and detailed results.
Conclusion
The accuracy and variability of DNA test results for ancestry are influenced by both subjective factors and the limitations of current scientific knowledge. While results may sometimes change, these changes often reflect improvements in the analysis rather than changes in the individual's genetic makeup. To get the most accurate and reliable results, it is important to consider the raw data and the ongoing improvements in the scientific methodologies used by DNA testing companies.