Certified Pediatric Hematology Oncology Nurse (CPHON) Practice Exam 2025 - Free CPHON Practice Questions and Study Guide

A positive Coombs direct test indicates the presence of antibodies bound to the surface of red blood cells, which is a hallmark finding in autoimmune hemolytic anemia (AIHA). In this condition, the immune system mistakenly produces antibodies that attack and destroy the body's own red blood cells, leading to hemolysis (the breakdown of red blood cells). The Coombs test detects these antibodies, confirming the autoimmune nature of the hemolytic process.

In contrast, elevated haptoglobin typically occurs as a response to hemolysis, where haptoglobin binds free hemoglobin released from destroyed red blood cells, but it does not specifically indicate an autoimmune reaction. Increased hemoglobin would suggest improvement in red blood cell mass and is not a characteristic of AIHA itself. A decreased reticulocyte count would indicate inadequate production of new red blood cells, which is not aligned with the expected compensatory response seen in hemolytic anemia where the reticulocyte count is often elevated. Thus, the positive Coombs direct test stands out as the specific finding that points towards the autoimmune mechanism at play in AIHA.