WHAT OLDER PATIENTS SHOULD KNOW ABOUT BLOOD TEST RESULTS

Medically Reviewed by Dr. Sony Sherpa (MBBS) - August 9, 2024

Regular health check-ups are crucial at every stage of life, yet they become even more vital as we age. Blood tests are key features of these annual check-ups, being a powerful tool for assessing overall health status. Valuable insights gleaned from blood test results help healthcare professionals detect potential issues early and tailor treatment plans accordingly.

Interpreting blood test results for older patients is often challenging and requires a nuanced approach due to age-related changes in blood chemistry. Common examples include values for blood glucose, erythrocyte sedimentation rate, and thyroid stimulating hormone, which are frequently observed to be higher in older individuals.

A few additional points to keep in mind:

• The content provided in this article is for informational purposes and should not be used for diagnosing or treating a health problem or disease. Always talk to your doctor about your blood test results. They can help you understand what the results mean and whether any further testing or treatment is needed.
• The definition of an "older" patient depends on specific parameters and factors such as gender. Therefore, it is best to check with your doctor if this applies to you.
• Be informed of the medications you are taking. Some medications can affect blood test results.
• Let your doctor know about any underlying health conditions you have. These conditions can also affect blood test results.
• Eat healthy and exercise regularly as appropriate for your age and health status. This can help to keep your blood test results within normal ranges.
• Get regular blood tests, even if you feel healthy. This is the best way to detect any changes in your blood test results early.

In this guide, we will delve into the importance of regular blood tests, how to interpret the results, and unique considerations for older patients.

Why Blood Test Values Change As One Ages

Blood chemistry is known to change with age, impacting various parameters measured in routine blood tests. These are often normal signs, yet it is crucial to be aware of them to avoid unnecessary concern or oversight.

One of the main problems with interpreting elderly blood test results is that there are no true standard ranges for older individuals. Doctors often adjust the average ranges for healthy adults to compensate and instead pay more attention to abnormal results across the board.

Common age-related changes in blood test results include:

• Hormonal fluctuations
• Lower blood cell counts
• Alterations in liver and kidney function

These changes typically arise due to declining reproductive hormones, a reduced metabolic rate, and a higher collection of aged cells. This leads to age-related metabolic and immune changes that can affect the blood test results and treatment of elderly individuals.

How Blood Test Results are Used to Reach a Diagnosis in the Elderly

It is important to note that unusual results do not necessarily confirm any diagnosis and could be the result of normal age-related fluctuations. A doctor is required to monitor an elderly patient for some time and take their entire history into account before they are able to reach a firm diagnosis.

Reasons a medical professional may be cautious when interpreting elderly blood test results include:

• Multiple chronic conditions: Elderly patients are more likely to have multiple chronic conditions, such as heart disease, diabetes, and arthritis. These conditions can interact with each other and make it difficult to diagnose a new condition. For example, an overweight patient with heart disease may experience shortness of breath from either heart failure, pneumonia, or excess weight that impacts the respiratory tract.
• Difficulty communicating symptoms: Seniors may have more difficulty communicating their symptoms or medical history than younger individuals. This may be due to cognitive impairment, hearing loss, or language barriers. It is important for doctors to take the time to listen carefully to elderly patients and ask clarifying questions.
• Medications: Polypharmacy (taking multiple medications and supplements) is common among elderly patients. These can interact with one another, reduce their potencies, and cause side effects. Doctors need to be aware of all of the medications and supplements a patient is taking in order to make an accurate diagnosis.
• Age-related body changes: The body undergoes many changes with age that can mimic symptoms or show up on test results and hinder diagnosis. These changes can also affect the way that seniors respond to treatment. Elderly patients often eat less, drink less fluids, and have lower hormone levels, which commonly promotes less muscle mass and more fat mass and affects the way medications are metabolized.

Blood Test Parameters Requiring Special Attention in Older Patients

Whenever a check-up is due, a skilled physician will likely listen to any current complaints a patient may have and assess their medical history to get a full understanding of their current state of health.

Once they have a good idea, they may order some blood tests to follow through. Here are some of the most common blood tests used to track health conditions in the elderly:

• Complete blood count (CBC)
• Basic metabolic panel (BMP)
• Comprehensive metabolic panel (CMP)
• Erythrocyte sedimentation rate test (ESR test)
• Thyroid function test

Each of these tests show standard deviations in older patients that are highlighted in the below blood test result charts alongside factors that can influence them.

Age-Related Changes in a Complete Blood Count

A complete blood count checks the levels of cells that make up the blood.^[1]

It is used in standard routine health check-ups to understand common symptoms like bruising, fatigue, and fever, as well as to assess patients at risk of anemia or follow-up on those being treated for cancer or cardiovascular conditions.

Complete Blood Count (CBC)	Adults	Elderly	Variation
Red Blood Cell Count (cells/mcL)	4.5-5.9 million (men) 4.1-5.1 million (women)	4.2-5.6 million (men) 3.8-5.8 million (women)	Lower
White Blood Cell Count (cells/mcL)	4500-11000	3400-9600	Lower
Hemoglobin (Hgb) (g/dL)	14-17.5 (men) 12.3-15.3 (women)	13.1-16.6 (men) 11.6-14.6 (women)	Lower
Hematocrit (Hct) (%)	41.5-50.4 (men) 35.9-44.6 (women)	40-48.9 (men) 34.5-43.2 (women)	Lower
Mean Corpuscular Volume (MCV) (fL)	80-96	-	-
Platelet Count (PLT) (cells/mcL)	150 000-400 000	135 000-371 000	Lower

As shown above, the majority of results from a CBC show slightly lower values in elderly patients. In healthy patients, this is a sign of a lower metabolic rate, an aged immune system, and reduced food and fluid intake. Elderly bone marrow produces fewer red blood cells and immune cells, and both types naturally have a shorter lifespan.

Anemia. A lower hemoglobin, hematocrit, or red blood cell count is often misinterpreted as anemia. While anemia is more common amongst the elderly, it is not likely that a lower score on a CBC is a direct indication. To give an idea, studies show that the prevalence of anemia increases to 10% in those over 65 years and can be as much as 20% in those over 80^[2]. It is also often observed as a symptom at critical stages of other diseases, such as kidney disease, or transient after an infection or major surgery.

Medication Use. Since immunosuppressants and blood thinners are often prescribed to the elderly, white blood cell and platelet counts are mostly reported to be lower than the above averages. Those on corticosteroids, chemo drugs, painkillers, and other over-the-counter medications should double-check abnormally low test results with their doctor first before worrying.

Basic Metabolic Differences in the Elderly BMP

As the name suggests, a basic metabolic panel (BMP) blood test measures blood glucose, electrolytes, and protein waste products in the blood that give insight into one’s overall metabolism, chemical balance, and kidney function.^[3]

Basic Metabolic Panel (BMP)	Adults	Elderly	Variation
Glucose (mmol/L)	3.9-7.8	-	Higher variance
Sodium (mmol/L)	135-145	-	-
Potassium (mmol/L)	3.5-5.1	-	-
Chloride (mmol/L)	98-107	-	-
Bicarbonate (mmol/L)	22-29	-	-
BUN (mmol/L)	2.14-7.14	2.14-8.57	Higher
Creatinine (mg/dL)	0.7-1.3 (men) 0.5-1.1 (women)	0.9-1.49 (men) 0.6-1.2 (women)	Higher

Most results in a metabolic panel will look the same between adults over and under 60 years of age, with blood glucose, creatinine, and BUN levels showing slight deviations in healthy seniors.

Glucose Variances. Due to age-related changes, it is possible to see higher variances in blood glucose levels that may deviate from the adult range. This is especially true of older women due to the abrupt hormonal decline seen in menopause, yet it tends to apply to elderly men over 70 as well. Diabetes may only be suspected if consistent unusual results are seen at check-ups coupled with other symptoms. Luckily, symptoms of diabetes are easy to distinguish from normal aging^[4].

Sodium and Potassium. Seniors are often susceptible to fluctuations in blood levels of sodium and potassium, with low sodium (hyponatremia) and high potassium (hyperkalemia) being a relatively common scenario^[5]. These are often ascribed to hormonal changes that cause aged individuals to drink less and hold more water, causing blood sodium to become diluted. Reduced kidney function and various medications, including diuretics, may cause potassium levels to become further unbalanced (beyond sodium dilution).

Creatinine and BUN. Creatinine and Blood Urea Nitrogen (BUN) are common indicators of kidney function that can be higher or lower in healthy seniors. It is usual for their levels to increase as one begins to age, as this correlates with slower kidney clearance of these protein waste products from the blood^[6]. This is also common after surgery^[7]. As one reaches advanced age, the levels may decline, which has been associated with age-related frailty and muscle loss.^[8]

Medications can also alter the results and make them an unreliable indicator of kidney function. When a patient is in this position, the doctor will make use of an estimated Glomerular Filtration Rate (eGFR) instead.^[9]

Comprehensive Metabolic Panel and Elderly Liver Function

A comprehensive metabolic panel (CMP) combines a BMP with a liver function test to give a deeper insight into overall metabolic health. A liver function test shows extra electrolytes, total blood proteins, bilirubin, and liver enzymes.

Comprehensive Metabolic Panel (CMP)	Adults	Elderly	Variation
Albumin (g/dL)	3.4-5.4	-	Same or Lower
Total protein (g/dL)	6.0-8.3	-	Same or Lower
Calcium (mmol/L)	2.15-2.55	-	-
Phosphorus (mmol/L)	0.81-1.45	-	-
Alkaline Phosphatase (ALP) (U/L)	44-147	-	Same or Higher
Alanine Aminotransferase (ALT) (U/L)	<40	-	Same or Higher
Aspartate Aminotransferase (AST) (U/L)	<40	-	Same or Higher
Bilirubin (µmol/L)	<21	-	Same or Higher

Most of the markers on an elderly CMP are similar to those seen in adults, with occasional fluctuations in protein and liver enzyme markers, as discussed below.

Albumin, a protein synthesized by the liver, is another vital marker. Reduced albumin and total protein levels may signify malnutrition or liver disease in younger patients. Declining albumin levels in the elderly are generally linked with:

• Muscle loss
• Inflammation due to infections and surgery
• Age-related changes in liver or kidney function
• Diet

Levels below 3.8g/dL are associated with a higher risk of surgical complications in those with hip fractures^[10], while levels below the normal values can be a sign of frailty and overall mortality risk, if prolonged.

Liver Enzymes. While usually insignificant, liver enzymes and bilirubin levels are known to gradually increase with age and may seem elevated when compared to a younger person’s results. This is a healthy sign of aging and still usually falls far beneath the peak cut-off value for liver disease and related problems.^[11]

Testing for Age-Related Inflammatory Changes

Various markers are used to assess inflammation in those with arthritis or similar inflammatory conditions, such as erythrocyte sedimentation rate and C-Reactive Protein levels. In the elderly, these markers are often higher and are not necessarily a sign of disease, usually indicating age-related changes in immune function.

Blood Test Markers Assessing Inflammation	Adults	Elderly	Variation
Erythrocyte Sedimentation Rate (ESR) (mm/hr)	0-15 (men) 0-20 (women)	8-40 (men) 8-45 (women)	Higher
C-Reactive Protein (CRP) (mg/L)	>3	>5	Higher

Erythrocyte sedimentation rate (ESR) tests measure how rapidly red blood cells segregate from the rest of the serum when treated to prevent clotting. ESRs are known to increase by 0.22mm/hr every year from the age of 20 and are higher in women than in men. As a result, they can appear almost double in healthy elderly patients and are not recommended as a standalone test to assess inflammation. If exceedingly high, an older individual may be suffering from arthritis or another systemic inflammatory condition. ^[12]

C-Reactive Protein in a blood test panel indicates the level of CRP in the blood. CRP is an acute-phase protein released by the liver in response to inflammatory events, such as infection and injury, to facilitate an optimal immune reaction. Elderly individuals and women may have higher general CRP levels. In the elderly, this has been associated with natural aging processes, such as cognitive decline, muscle loss and eventual frailty. CRP levels may only be a cause for concern when CRP levels reach the high end of the spectrum at over 9mg/L. This is associated with a high risk for developing age-related conditions, such as dementia, heart disease or arthritis. Further testing is required to rule out potential causes.

Senior Thyroid Function Tests

A thyroid function test monitors the thyroid hormone levels to determine the health of the thyroid glands and how it affects the body's general metabolism.

Thyroid Function Test	Adults	Elderly	Variation
TSH (mIU/L)	0.4-5	0.55-5.25	Same or Higher
FT4 (pmol/L)	10-25	-	Same or Lower
FT3 (pmol/L)	3.5-6	-	Same or Lower
Tg (ng/mL)	<55	-	-
TPOAb (IU/mL)	<35	-	-
TgAb (IU/mL)	<115	-	-

Across studies, elderly patients were shown to have a higher baseline level of thyroid stimulating hormone (TSH) and a lower average baseline for thyroid hormones FT3 and FT4^[13]. This suggests that aging is linked to diminished thyroid function and raises the risk of hypothyroidism. Symptoms such as fatigue and weakness, often associated with aging, should not be overlooked if they have a sudden onset or are extreme, as they may indicate hypothyroidism.

Other parameters of thyroid function are equitable to results seen in younger adults, and if unusually high, an autoimmune thyroid condition may be suspected.^[14] 

The Impact of Drug Interactions on Blood Test Results

Blood tests can be used to measure the levels of different medicines in the blood and can sometimes show if two medications are not working well together. This is because some medicines can cross-react, affecting the way in which each is metabolized as well as their blood levels. This can make one or both medicines less effective, or it can increase the risk of side effects.

There are two main types of drug interaction:

• Pharmacodynamic interactions: These occur when two drugs have overlapping mechanisms, interacting with the same target in the body. This can result in either an increased or decreased effect of one or both drugs. For example, warfarin may be prescribed to thin the blood, and NSAIDs (non-steroidal anti-inflammatories) may be prescribed to reduce pain. NSAIDs can increase the risk of bleeding for those on warfarin through overlapping anticoagulant properties that enhance warfarin’s blood-thinning effects.
• Pharmacokinetic interactions: These happen when one drug affects the way another drug is absorbed, distributed, metabolized, or excreted by the body. This makes one or both drugs less or more effective and can lead to side effects.  For instance, the antiarrhythmic drug amiodarone can interfere with the metabolism of statins and lead to muscle toxicity.

These two types of drug interactions frequently overlap with one another across a wide spectrum of medications. It is vital for doctors to take them into consideration when prescribing multiple medications to elderly patients or adding to a long prescription list.

If a patient is taking two medications that are known to interact, the doctor may use blood tests to monitor the levels of both medications. If the levels of one or both are outside of the normal range, this may be a sign of a drug interaction.

Your doctor will act accordingly to minimize drug-drug interactions. This may involve adjusting the dosage of one or both medicines, switching to different medicines, or avoiding the interaction altogether by asking you to take them several hours apart or cutting down on your prescription list.

It is important to note that not all drug interactions are serious. Some drug interactions are mild and only cause minor side effects. Other drug interactions can be more serious and can lead to hospitalization or even death.  If symptoms persist after a prescription has been adjusted accordingly, the doctor may proceed to investigate with follow-up tests to check for signs of disease.

Conclusion

Regular blood tests are invaluable for monitoring the health of older patients. Understanding age-related changes is essential to prevent unnecessary concern. Certain parameters are known to change in the elderly that can mimic signs of disease, yet they are not necessarily a cause for concern. These include a lower blood cell count, higher blood waste products, reduced thyroid function, and increased overall bodily inflammation.

Medications, comorbidities, and frailty all pose challenges in interpreting elderly blood test results. This highlights the importance of consulting with a doctor, asking the right questions at appointments, and supplying them with accurate information regarding your medical history before they can arrive at an accurate diagnosis.

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