As part of our ongoing efforts to help improve our reporting, we recently 
announced an update that changes how each keyword’s 1-10 numeric 
Quality Score (QS) is reported in AdWords. This reporting update will tie your 1-10 numeric Quality Score more closely to its three key sub factors: 
expected clickthrough rate, 
ad relevance, and 
landing page experience.
This is only a change to how Quality Score is reported. It does not change how Quality Score is calculated in real-time for each auction, and thus won't have any direct effect on your ad performance. Therefore, unless you have automated rules or Adwords Scripts tied directly to your reported 1-10 QS, your ads should continue to behave as they did before.
If you use the 
qualityScore field from 
AdGroupCriterionService or QualityScore from 
CRITERIA_PERFORMANCE_REPORT, 
KEYWORDS_PERFORMANCE_REPORT or 
MANAGED_PLACEMENTS_PERFORMANCE_REPORT to adjust bids, then you may notice that the keywords that meet your criteria may change after this update.
We hope this change makes it easier for you to improve your ads and to know when your changes are working. If you have questions or feedback, please visit us on our 
official forum.
 Anash P. Oommen, AdWords API Team
Anash P. Oommen, AdWords API Team