Another Benefit of Warfarin Therapy: Early Diagnosis of Gastrointestinal Neoplasia

Which studies are most useful in the workup of suspected bleeding in a patient who is receiving warfarin therapy?

Warfarin is a proverbial double-edged sword. If you have experienced a deep venous thrombosis, a pulmonary embolus, atrial fibrillation, or certain stroke risks, or have a ventricular thrombus or mechanical heart valve—you run prohibitive risks without it. Conversely, it has a narrow therapeutic window and persons taking it can bleed and do so vigorously! One must not forget that warfarin’s first utilization was as a rat poison. A recent “Top Paper”¹ has found another important benefit of warfarin therapy—early diagnosis of gastrointestinal (GI) lesions that are or may become malignant.

EARLY DETECTION OF GI BLEEDING SOURCES

Three thousand and eighteen patients taking warfarin were identified. The cohort was monitored with complete blood cell (CBC) counts, and if the count declined—that is, the hemoglobin level or hematocrit decreased more than 5 units, or the mean cell volume (MCV) dropped to less than 80 fL—patients were contacted and offered workup for possible bleeding sources.

Eighty-two persons with anemia or a change consistent with the above parameters were studied by upper and lower GI endoscopy. GI malignancies were discovered in 11 patients. Ten had colorectal cancers and one an esophageal cancer. Another 25 patients had non-malignant bleeding sources. Included in this latter group were tubular adenomas, villous adenomas, erosions, angiodysplasias, ulcers, and one Dieulafoy’s lesion in the duodenum. Obviously, adenoma removal followed by appropriate surveillance may prevent cancer later.

WHAT’S NEW HERE

I was always taught that the development of anemia or GI bleeding in a patient receiving warfarin warranted further study. That part of the results is not new. But, the specific listing of malignancies as well as other lesions in this population is a valuable reminder of the importance of that workup.

I would also add another marker to be evaluated in persons receiving warfarin therapy. When the CBC count provides a red cell distribution width (RDW), use it. It is a correlate of the variation in individual red cell size. Iron deficiency evolves in a predictable manner. The first event that occurs is an increase in RDW—even before changes in MCV and hemoglobin. In fact, it is an increase in RDW, anemia, and only then microcytosis as iron deficiency intensifies. When we forget the order of progression, and wait for the MCV or hemoglobin to decline, we delay the diagnosis of iron deficiency or blood loss inappropriately. Whenever I check the INR for warfarin effect, I will pay close attention to CBC parameters and look for GI blood loss when indicated.