1374
In this group of relatives , a low free protein S level was the most reliable predictor of a PROS1 gene defect ( sensitivity 97 . 7 % , specificity 100 % ) .
 PROS1 gene defect
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Disease 
Text: {0} 
Answer:
 PROS1 gene defect