Database: thrombosis_prediction
Question: How many patients have a normal level of anti-ribonuclear protein and have been admitted to the hospital?
SQL: SELECT COUNT(DISTINCT T1.ID) FROM Patient AS T1 INNER JOIN Laboratory AS T2 ON T1.ID = T2.ID WHERE T2.RNP = 'negative' OR T2.RNP = '0' AND T1.Admission = '+'