To find out if the symbol is suspicious use IsSuspicious property of CharParams object. Use  “RecognizedTextProcessing” sample from the Code Samples Library for the code sample.

You may check the confidence level in % with Voting API. To do so, please specify

DocumentProcessingParams.PageProcessingParams.RecognizerParams.ExactConfidenceCalculation = true;

during the recognition. 

After the recognition, you will be able to access CharConfidence property of the CharacterRecognitionVariant and PlainText objects.