What is a Quality Score in Sequencing?
Q Score Definition
The sequencing quality score of a given base, Q, is defined by the following equation:
Q = -10log10(e)
where e is the estimated probability of the base call being wrong.
Higher Q scores indicate a smaller probability of error.
Lower Q scores can result in a significant portion of the reads being unusable. They may also lead to increased false-positive variant calls, resulting in inaccurate conclusions.
A quality score of 20 (Q20) represents an error rate of 1 in 100 (meaning every 100 bp sequencing read may contain an error), with a corresponding call accuracy of 99%.
When sequencing quality reaches Q30, virtually all of the reads will be perfect, with no errors or ambiguities. This is why Q30 is considered a benchmark for quality in next-generation sequencing (NGS).
参考
