AKT-2380

A 61-year-old woman presents to your clinic with a bowel issue. She has a history of irritable bowel syndrome and has experienced occasional abdominal bloating and changes in stool consistency for many years. However, over the past four weeks, she has noticed a significant increase in symptoms, including daily loose and frequent stools. She denies any rectal bleeding and cannot recall experiencing loose stools for this extended period before.
Upon examination, she appears well, with a soft and non-tender abdomen and no palpable masses. Rectal examination is normal, and her weight is comparable to her last visit a year ago.
Which of the following tests would you suggest for this patient?