NU 611 Unit 3 diagnostic workup rationale example

Diagnostic Workup Rationale for Microcytic Anemia Found at a Routine Visit in a 58-Year-Old Man

Student Name

Department of Nursing, Herzing University

NU 611: Clinical Decision-Making

Instructor Name

February 3, 2026

Diagnostic Workup Rationale for Microcytic Anemia Found at a Routine Visit in a 58-Year-Old Man

Starting Point: What Was Known Before Testing

A composite 58-year-old man, a delivery driver, had a complete blood count drawn at a routine visit because he mentioned feeling more tired than usual for about four months. The result showed hemoglobin of 10.9 g/dL, a mean corpuscular volume of 74 fL, and a platelet count at the upper end of normal. He reports no visible bleeding, no black stools, no change in bowel habits, and no abdominal pain. He takes naproxen most days for back pain. He has never had a colonoscopy. He eats meat several times a week. Examination shows pale conjunctivae and is otherwise unremarkable, including a nontender abdomen.

Before any further testing, the candidates were held as follows. Iron deficiency anemia was held as the leading explanation, strongly: microcytosis with a borderline-high platelet count fits it, and dietary deficiency is unlikely in a man eating meat regularly, which makes blood loss the probable mechanism. Within that, gastrointestinal blood loss was held as the likely source, and colorectal neoplasia was held as a serious possibility that could not be dismissed at his age and screening history. Anemia of chronic inflammation was held as possible but less likely, because he reports no inflammatory illness. Thalassemia trait was held as unlikely, because a lifelong trait would usually have appeared on earlier blood counts, which he recalls as normal.

Test One: Serum Ferritin

Candidate addressed: iron deficiency, against anemia of chronic inflammation and thalassemia trait. Ferritin was chosen over the full iron panel as the first step because it is the single most informative laboratory test for iron deficiency; in an overview of laboratory studies, a low ferritin carried a far stronger likelihood ratio than serum iron, transferrin saturation, or red cell indices (Guyatt et al., 1992).

If positive, meaning low: iron deficiency is confirmed, and the question shifts entirely from whether he is iron deficient to why. Current gastroenterology guidance uses a ferritin cutoff of 45 ng/mL in patients with anemia, rather than a lower threshold, to avoid missing iron deficiency (Ko et al., 2020). If negative, meaning normal or high: iron deficiency becomes less likely, though not excluded, because ferritin rises with inflammation. In that case transferrin saturation and C-reactive protein would be added to separate true iron sufficiency from masked deficiency. Cost and burden: one blood draw, low cost, results within a day.

Test Two: Bidirectional Endoscopy

Candidate addressed: the source of iron loss, specifically colorectal cancer, gastric or duodenal ulceration from daily naproxen, and upper gastrointestinal malignancy. In men and postmenopausal women with confirmed iron deficiency anemia, the recommended evaluation is both upper endoscopy and colonoscopy rather than colonoscopy alone, because lesions are found in both tracts and occasionally in both at once (Ko et al., 2020).

If positive: a bleeding lesion is identified and treated, and biopsies establish its nature. A finding in one tract does not end the examination of the other, because a benign ulcer in the stomach does not exclude a colon tumor. If negative: the most dangerous sources are excluded with reasonable confidence, and attention turns to small bowel sources and malabsorption. Cost and burden: this is the most invasive and expensive step, requiring bowel preparation, sedation, a day off work, and a driver. Those burdens are real for a man who drives for a living and are discussed with him directly, but they do not change the recommendation, because the consequence of missing colorectal cancer outweighs them.

Test Three: Celiac Serology and Helicobacter pylori

Candidates addressed: malabsorption from celiac disease, and Helicobacter pylori infection as a contributor to iron deficiency and ulceration. Tissue transglutaminase IgA with a total IgA level was ordered because celiac disease is a recognized cause of otherwise unexplained iron deficiency, and noninvasive testing is suggested before routine duodenal biopsy (Ko et al., 2020). If positive, duodenal biopsies are taken at the planned upper endoscopy; if negative, celiac disease becomes unlikely in a patient with normal IgA. Helicobacter pylori testing was planned as part of the upper endoscopy through gastric biopsy, which avoids a separate stool or breath test and the need to stop acid-suppressing medication beforehand. If positive, treatment is given; if negative, the infection is removed as a contributor.

Sequencing

Ferritin comes first because every later test depends on it: endoscopy is not justified by microcytosis alone. Celiac serology is drawn at the same time as ferritin, because it costs little and its result determines whether biopsies are needed during endoscopy. Endoscopy follows as soon as ferritin confirms deficiency, scheduled within weeks rather than months. Oral iron is started once ferritin is confirmed low, because waiting for endoscopy prolongs symptoms, and a rise in hemoglobin on iron is also informative. Naproxen is stopped immediately and acetaminophen offered for back pain, since that decision does not depend on any result.

Tests Considered and Declined

Fecal occult blood testing was declined. A positive result would add nothing, because endoscopy is already indicated, and a negative result would not remove the indication, because bleeding from a lesion is often intermittent. A test that cannot change management either way does not earn a place in the plan. Hemoglobin electrophoresis was declined at this stage, because thalassemia trait is unlikely given his history of normal counts and the plan would not change unless ferritin returned normal. A bone marrow examination was declined because the pattern is typical, the other cell lines are normal, and the noninvasive tests are expected to explain the anemia. Abdominal computed tomography was declined because it would expose him to radiation and cost without addressing the most likely sources, which are mucosal and best seen endoscopically.

Stopping Rule

The workup ends when a lesion sufficient to explain the iron loss is found and treated and his hemoglobin and ferritin recover on iron replacement. If bidirectional endoscopy and celiac testing are unrevealing and he responds fully to iron, further investigation of the small bowel is not automatic and would be discussed with gastroenterology based on whether the anemia recurs after iron is stopped. If he does not respond to oral iron, the reasoning restarts: adherence, ongoing loss, malabsorption, and a second cause of anemia would each be revisited. Iron deficiency, as Camaschella (2015) emphasizes, is a sign whose cause must be found, not a diagnosis that ends with a prescription.

References

Camaschella, C. (2015). Iron-deficiency anemia. New England Journal of Medicine, 372(19), 1832-1843. https://doi.org/10.1056/NEJMra1401038

Guyatt, G. H., Oxman, A. D., Ali, M., Willan, A., McIlroy, W., & Patterson, C. (1992). Laboratory diagnosis of iron-deficiency anemia: An overview. Journal of General Internal Medicine, 7(2), 145-153. https://doi.org/10.1007/BF02598003

Ko, C. W., Siddique, S. M., Patel, A., Harris, A., Sultan, S., Altayar, O., & Falck-Ytter, Y. (2020). AGA clinical practice guidelines on the gastrointestinal evaluation of iron deficiency anemia. Gastroenterology, 159(3), 1085-1094. https://doi.org/10.1053/j.gastro.2020.06.046