Testing Practices, Interpretation, and Diagnostic Evaluation of Iron Deficiency Anemia by US Primary Care Physicians

Abstract

Importance: Recognition of iron deficiency anemia (IDA) is important to initiate timely evaluation for gastrointestinal tract cancer. Retrospective studies have reported delays in diagnostic evaluation of IDA as a common factor associated with delayed diagnosis of colorectal cancer.

Objective: To assess how US primary care physicians (PCPs) approach testing for anemia, interpret iron laboratory studies, and refer patients with IDA for gastrointestinal endoscopy.

Design, setting, and participants: This survey study, conducted in August 2019, included members of the American College of Physicians Internal Medicine Insiders Panel, a nationally representative group of American College of Physicians membership, who self-identified as PCPs. Participants completed a vignette-based survey to assess practices related to screening for anemia, interpretation of laboratory-based iron studies, and appropriate diagnostic evaluation of IDA.

Main outcomes and measures: Descriptive statistics based on survey responses were evaluated for frequency of anemia screening, correct interpretation of iron laboratory studies, and proportion of patients with new-onset IDA referred for gastrointestinal tract evaluation.

Results: Of 631 PCPs who received an invitation to participate in the survey, 356 (56.4%) responded and 31 (4.9%) were excluded, for an adjusted eligible sample size of 600, yielding 325 completed surveys (response rate, 54.2%). Of the 325 participants who completed surveys, 180 (55.4%) were men; age of participants was not assessed. The mean (SD) duration of clinical experience was 19.8 (11.2) years (range, 1.0-45.0 years). A total of 250 participants (76.9%) screened at least some patients for anemia. Interpretation of iron studies was least accurate in a scenario of a borderline low ferritin level (40 ng/mL) with low transferrin saturation (2%); 86 participants (26.5%) incorrectly responded that this scenario did not indicate IDA, and 239 (73.5%) correctly identified this scenario as IDA. Of 312 participants, 170 (54.5%) recommended bidirectional endoscopy (upper endoscopy and colonoscopy) for new IDA for women aged 65 years; of 305 respondents, 168 (55.1%) recommended bidirectional endoscopy for men aged 65 years.

Conclusions and relevance: In this survey study, US PCPs' self-reported testing practices for anemia suggest overuse of screening laboratory tests, misinterpretation of iron studies, and underuse of bidirectional endoscopy for evaluation of new-onset IDA. Both misinterpretation of iron studies and underuse of bidirectional endoscopy can lead to delayed diagnosis of gastrointestinal tract cancers and warrant additional interventions.

Conflict of interest statement

Conflict of Interest Disclosures: Dr Saini reported receiving research and employment support from the Department of Veterans Affairs. No other disclosures were reported.

Figures

Figure 1.. Rates of Obtaining Complete Blood Counts (CBCs) for Detection of Anemia in Asymptomatic Patients by Age, Sex, and Pregnancy Status for Healthy Patients Establishing Care With a Primary Care Physician

Data are based on survey responses of 325 primary care physicians reporting recommendations of 1 CBC, repeated CBCs, or no CBC. For pregnant women, there were 220 respondents because primary care physicians who did not provide care to pregnant women were excluded.

Figure 2.. Interpretation of Iron Studies for Diagnosis of Iron Deficiency Anemia in 4 Scenarios With Different Combinations of Ferritin Levels and Transferrin Saturation (TSAT)

Details of the scenarios are given in the Questionnaire Design subsection of the Methods section.

Figure 3.. Initial Diagnostic Evaluation Recommended by Respondents for Patients With New-Onset Iron Deficiency Anemia and Negative Celiac Serologic Test Results by Age and Sex

EGD indicates esophagogastroduodenoscopy.