Priority Topic: Anemia

Key Feature 5: Consider and look for anemia in appropriate patients (ex: those at risk for blood loss [those receiving anticoagulation, elderly patients taking a nonsteroidal anti-inflammatory drug]) or in patients with hemolysis (mechanical valves), whether they are symptomatic or not, and in those with new or worsening symptoms of angina or CHF. 
Skill: Clinical Reasoning, Selectivity
Phase: Hypothesis generation, Investigation

Key Feature 7: As part of well-baby care, consider anemia in high-risk populations (ex: those living in poverty) or in high-risk patients (ex: those who are pale or have a low-iron diet or poor weight gain). 
Skill: Clinical Reasoning, Selectivity
Phase: Hypothesis generation

Key Feature 9: In anemic patients with menorrhagia, determine the need to look for other causes of the anemia. 
Skill: Clinical Reasoning
Phase: Hypothesis generation

Anemia is something we are taught not to screen the general population for. National and provincial medical colleges in Canada do not have screening guidelines for it (as far as I'm aware), and although patients may think they often may have it, they often don't, although it is not an uncommon problem per se. Is there anyone who actually warrants being investigated for anemia? 
 
Let's separate this discussion into diagnostic testing for anemia and screening for anemia.

If we are concerned that a patient may be presenting with symptoms or signs of anemia, this would warrant a diagnostic CBC to rule in or rule out that possibility. According to the UpToDate article, Approach to the adult patient with anemia (2017), the symptoms and signs of anemia present for two reasons: 

1. Decreased oxygen delivery: "The primary symptoms include exertional dyspnea, dyspnea at rest, varying degrees of fatigue, and signs and symptoms of the hyperdynamic state such as bounding pulses, palpitations, and a roaring pulsatile sound in the ears. More severe anemia may lead to lethargy, confusion, and potentially life-threatening complications such as congestive failure, angina, arrhythmia, and/or myocardial infarction." 
2. Hypovolemia: "Anemia induced by acute bleeding is associated with the added complication of intracellular and extracellular volume depletion. The earliest symptoms include easy fatigability, lassitude, and muscle cramps. This can progress to postural dizziness, lethargy, syncope, and, in severe cases, persistent hypotension, shock, and death."

The signs and symptoms associated with anemia are common to other disease processes, so anemia may not be the culprit, or at least the only culprit. The patient may already carry a diagnosis of congestive heart failure or coronary artery disease manifesting with angina that may be the aggravant. However, in these patients with other potentially responsible medical conditions, if they experience a worsening in their baseline degree of these symptoms, it would be prudent to test for anemia as it may be co-occuring and having a compounding effect.

Now let's consider who warrants being screened for anemia. When we discuss screening for any disease, it means the patient being tested does not have symptoms or signs of the disease being tested for, but they may actually have it and it may just not be bad enough (yet) to be overt. The decision to screen for a disease is a big consideration, must take into account the risks vs benefit for individuals and the health care system as a whole, and there can be very positive, negative, and unknown ramifications. Choosing Wisely Canada, an organisation that promotes mindful use of health care resource stewardship, has put out a list series of recommendations targeted to various groups of physicians. The fifth of its recommendations for Canadian family physicians is: "Don’t do annual screening blood tests unless directly indicated by the risk profile of the patient." They further explain this by saying, "There is little evidence to indicate there is value in routine blood tests in asymptomatic patients; instead, this practice is more likely to produce false positive results that may lead to additional unnecessary testing. The decision to perform screening tests, and the selection of which tests to perform, should be done with careful consideration of the patient’s age, sex and any possible risk factors." So are there risk factors that warrant screening for anemia? 

This Key Feature would suggest there are, and it points to screening those people who are host to the disease processes we would look for if a patient were instead first diagnosed with anemia. Based on this logic, I should be thinking about screening patients for anemia if they have the following risk factors, with CBC but also ferritin if I am screening them because they have a risk factor associated with iron-deficiency anemia (essentially the reverse DDx of causes for the various subtypes of anemia):

• Iron deficient diets (ex: young children who are older than 6 months of age and who consume excess breastmilk or formula that is not iron-fortified, or patients with a low socioeconomic status, poor nutritional status, who are vegetarian, or who consume significant quantities of alcohol)
• Poor iron absorption from diet (ex: inflammatory bowel disease, new diagnosis of celiac disease or H. pylori, history of gastric surgery)
• Patients who are pregnant
• High intensity athletes (increased cell turnover, resulting in faster depletion of stores)
• Patients with suspected lead poisoning
• Patients with chronic disease in whom anemia may be more consequential (ex: coronary artery disease, congestive heart failure, cardiac dysrhythmia)*
• Patients with a known source of more than minimal bleeding**
• Patients with reason to be at risk of hemolysis (ex: patients with a mechanical heart valve, patients with sickle-cell anemia)
• Patients with possible hematopoeitic-compromising conditions (ex: chronic kidney disease, liver disease, hypothyroidism if not controlled or upon diagnosis, malignancy, myelodysplasia)
• Patients who take drugs that can cause anemia (ex: methotrexate)
• Probably others that are not also coming to my mind (aka as clinically indicated)

*I haven't seen this being mentioned anywhere, so is totally my own thought, but I wonder if having a psychiatric illness would fall under this category. Patients who are already battling depression and the low energy that can bring may be more susceptible to a secondary hit with anemia. Anemia can also provoke feelings of anxiety as the body is becoming less and less able to meet its oxygen demands. Anemia is on the differential diagnosis for patients presenting with symptoms of depression and anxiety, after all. My logic leads me to think they would qualify to be screened for anemia as well.

**Females of reproductive age having heavy menstrual cycles may be anemic secondary to having a heavy flow. But exactly how can one know that a patient's flow is heavy enough to be suspect or whether we should be looking for another cause? UpToDate has a table of questions I find helpful in determining this: