Chem Path Flashcards
What is chemical pathology
WHAT IS CHEMICAL PATHOLOGY?
• Chemical Pathology is the branch of pathology dealing with the biochemical basis of disease and the use of biochemical tests for diagnosis and management.
• It is also known as Clinical Biochemistry or Clinical Chemistry
Why are lab tests usually requested
The justification for discretionary testing is well summarised by answering some questions, state five of these questions
THE USE OF CLINICAL BIOCHEMISTRY TESTS
• Laboratory tests are most often requested for defined diagnostic purposes.
• The justification for discretionary testing is well summarised by answering the following question:
Why do I request this test?
2 What will I look for in the result?
3 IfI find what I am looking for, will it affect my diag-nosis?
4 How will this investigation affect my management of the patient?
5 Will this investigation ultimately benefit the
patient?
How often should a patient be investigated
HOW OFTEN SHOULD A PATIENT BE INVESTIGATED? This depends on the following:
1.How quickly numerically significant changes are likely to occur:
• for example, concentrations of the main plasma protein fractions are unlikely to change significantly in less than a week
2.Whether a change, even if numerically significant, will alter treatment:
• for example, plasma transaminase activities may alter within 24 h in the course of acute hepatitis, but, once the diagnosis has been made, this is unlikely to affect treatment.
• By contrast, plasma potassium concentrations may alter rapidly in patients given large doses of diuretics and these alterations may indicate the need to change treatment
State four purposes of lab tests
1.SCREENING
lab tests are used for mass screening (e.g., phenylketonuria and sickle cell in newborns). Usually done for plenty people .like a mass something. Usually done for people who are asymptomatic. Low dose ct scan is usually used as a screening test.
•screening asymptomatic patients (they don’t have symptoms. You’re just checking routinely.e.g., mammography, Here are some examples of screening in asymptomatic patients:
- Colonoscopy: Recommended for adults over a certain age (typically 50 years and older) to screen for colorectal cancer, even if they have no symptoms.
- Mammography: Used to screen for breast cancer in women, usually starting from age 40 to 50, depending on guidelines, before any symptoms such as lumps or pain develop.
- Prostate-Specific Antigen (PSA) Test: Used to screen for prostate cancer in men, typically over the age of 50, who do not have symptoms like difficulty urinating or blood in the urine.
- Pap Smear: A screening test for cervical cancer in women, usually starting at age 21, even if they have no symptoms.
- Blood Pressure Measurement: Regular screening for hypertension in adults, as high blood pressure often has no symptoms but increases the risk of heart disease and stroke.
- Lipid Profile: Blood tests to screen for high cholesterol levels, which can lead to cardiovascular disease, even if the patient is asymptomatic.
- Bone Density Scan (DEXA): Used to screen for osteoporosis in postmenopausal women and older adults, particularly those with risk factors, before any symptoms like fractures occur.
- HIV Testing: Recommended for all adults at least once and regularly for those at higher risk, even if they have no symptoms, to prevent the spread of the virus and manage the condition early.
- Diabetes Screening (HbA1c or Fasting Blood Glucose): Used to screen for type 2 diabetes in adults, particularly those with risk factors like obesity or a family history, even if they are asymptomatic.
- Lung Cancer Screening: Low-dose CT scans are recommended for long-term smokers or former smokers, typically over the age of 55, even if they do not have any respiratory symptoms.
These screenings aim to detect diseases early in asymptomatic individuals, improving the chances of successful treatment and reducing the risk of complications.), and
Screening Symptomatic patients (they have the symptoms and you want to check if they have the disease . stress ECG in patients with chest pain). Here are some additional examples of screening symptomatic patients:
- Blood Glucose Testing: For patients presenting with symptoms like excessive thirst, frequent urination, or unexplained weight loss, blood glucose tests are used to screen for diabetes.
- Electrocardiogram (ECG): In patients with symptoms like chest pain, palpitations, or shortness of breath, an ECG is used to screen for cardiac arrhythmias, ischemia, or myocardial infarction.
- D-Dimer Test: For patients with symptoms such as sudden shortness of breath or chest pain, a D-dimer test can be used to screen for pulmonary embolism or deep vein thrombosis.
- Thyroid Function Tests: In patients with symptoms such as fatigue, weight gain, or cold intolerance, thyroid function tests (e.g., TSH, T3, T4) are used to screen for thyroid disorders like hypothyroidism or hyperthyroidism.
- Chest X-ray: For patients with a cough, fever, or difficulty breathing, a chest X-ray is commonly used to screen for pneumonia, lung cancer, or other pulmonary conditions.
- Complete Blood Count (CBC): In patients with symptoms like fatigue, pallor, or frequent infections, a CBC is used to screen for anemia, infections, or hematologic disorders.
- Urinalysis: For patients presenting with symptoms
2.DIAGNOSIS
• They are used to confirm a diagnosis (e.g., coronary angiogram to confirm coronary artery disease in a patient with a positive stress electrocardiogram).
How to know if a test is for diagnosis or for screening symptomatic people:
Analyze the Clinical Context:
• If the patient is symptomatic and the test is ordered to identify the underlying cause of their symptoms, it is most likely a diagnostic test. • If the test is conducted despite the patient having symptoms, and it’s part of a routine evaluation or a risk assessment tool, it could be a screening test for an associated condition or to determine the extent of a known disease.
3.MONITORING TREATMENT
• They are used to monitor a patient’s disease status le.g., plasma glucose in a person with uncontrolled diabetes). So the person has a disease or has had the disease before and is coming to just check how far. This doesn’t apply to those with a family history of the disease but have never gotten it before.
- PROGNOSIS
• providing information on disease susceptibility. It is used to predict the risk or the disease course or the likelihood of disease progression
Certainly! Here are some MCQs focused on identifying when a test is used for prognosis:
A 62-year-old woman with stage II breast cancer undergoes a genetic test to determine her risk of cancer recurrence. This test is used to guide treatment decisions and predict long-term outcomes. What is the primary purpose of this test?
A) Screening
B) Diagnostic
C) Monitoring
D) Prognostic
Answer: D) Prognostic
Explanation: The genetic test is used to predict the risk of cancer recurrence and guide treatment decisions, which is characteristic of prognostic testing.
A 45-year-old man with diagnosed prostate cancer undergoes a PSA (Prostate-Specific Antigen) test every six months to assess the likelihood of disease progression and adjust treatment accordingly. What is the primary purpose of the PSA test in this context?
A) Screening
B) Diagnostic
C) Monitoring
D) Prognostic
Answer: C) Monitoring
Explanation: The PSA test is used to monitor the progression of prostate cancer in a patient with a known diagnosis, not to predict the disease course. It’s monitoring cuz you’re assessing disease progression to make changes to treatment plan but you don’t do this in prognosis. Prognosis, you’re checking risk to see what you can do long term not now
A 50-year-old woman with rheumatoid arthritis undergoes an anti-CCP (anti-cyclic citrullinated peptide) antibody test to evaluate the likelihood of severe disease progression and joint damage. What is the primary purpose of this test?
A) Screening
B) Diagnostic
C) Monitoring
D) Prognostic
Answer: D) Prognostic
Explanation: The anti-CCP antibody test is used to predict the severity and progression of rheumatoid arthritis, making it a prognostic test.
A patient diagnosed with heart failure has an echocardiogram to assess the current heart function and determine the appropriate treatment plan. What is the primary purpose of this echocardiogram?
A) Screening
B) Diagnostic
C) Monitoring
D) Prognostic
Answer: C) Monitoring
Explanation: The echocardiogram is used to monitor the function of the heart and guide ongoing treatment, rather than to predict future disease outcomes.
A 30-year-old woman with a newly diagnosed melanoma undergoes a staging scan to evaluate the extent of the disease and predict the likely outcome and response to therapy. What is the primary purpose of this staging scan?
A) Screening
B) Diagnostic
C) Monitoring
D) Prognostic
Answer: D) Prognostic
Explanation: The staging scan is used to assess the extent of melanoma and predict the disease’s progression and response to treatment, which is prognostic.
It’s prognostic cuz this person is newly diagnosed so your now trying to see how bad the disease is and predict the future outcome for the patient. If the person wasnt newly diagnosed, it would’ve been monitoring.
This example highlights when to choose “prognostic” as the correct answer:
- The staging scan for the newly diagnosed melanoma is being used not just to diagnose the extent of the disease but to predict how the disease might progress and how the patient might respond to therapy. This aligns with the purpose of a prognostic test, which is to provide information on the likely future course and outcome of the disease based on current findings.
In this context:
- Prognostic is the right choice because the scan is used to assess the extent of the disease and predict the patient’s future outcome.
This contrasts with monitoring, which would involve ongoing tests after the initial diagnosis to see how the disease evolves or responds to treatment over time.
Hhh
Let’s clarify the differences between prognostic and monitoring:
- Purpose: To predict the future course or outcome of a disease.
- When Used: Typically at or near the time of diagnosis.
- Example: A staging scan in a newly diagnosed cancer patient to determine how advanced the disease is and predict how the patient might fare in the future. This helps doctors understand the likely outcome (prognosis) and plan treatment.
- Purpose: To track the disease’s status and response to treatment over time.
- When Used: After a diagnosis has been made, during and after treatment.
- Example: Regular PSA tests in a prostate cancer patient who is already diagnosed, used to check if the disease is progressing or responding to treatment.
- Staging Scan for Melanoma: The scan is being done to evaluate the extent of the disease at the time of diagnosis and to help predict how the disease might progress and how well the patient might respond to treatment. This is why it’s considered prognostic—it’s helping to predict the future outcome.
- If this patient, after being diagnosed, were undergoing regular scans to check if the melanoma was getting worse or if the treatment was working, that would be monitoring.
Understanding when a test is predicting future outcomes (prognostic) versus tracking ongoing changes (monitoring) is key. Prognostic tests give an initial outlook, while monitoring tests keep track over time.
e.g. prognosis can be predicted by noting the degree of test abnormality
State five criteria for laboratory screening
LABORATORY SCREENING CRITERIA
1. There must be a high prevalence of the disease to justify the expense.
2. Significant morbidity and mortality must be associated with the disease if it is left untreated.
3. The disease must be detectable before symptoms surface in the patient.
4. An effective therapy must be available that is safe and inexpensive.
5. The test must be cost effective and easily performed in the laboratory.
Sequence of tests depends on several factors
State 3
In critical situations where immediate action is necessary, what type of test do you do first ?(a.the one with the highest yield,b. the one with the lowest yield,c. the one with the lowest risk,d. the one with the highest risk)
In non critical situations, when time allows and the patients condition allows for it, what kind of tests do you do first?(a. High risk and high yield. b. Less risk or lower yield c. High risk and low yield d. High yield and low risk )
Here’s a summary of the considerations and principles involved:
Sequence of Tests:
1. Dependence on Factors: • The choice of which test to conduct first depends on various factors such as the urgency of the situation, the risk involved, and the expected yield of the test (likelihood of providing useful information). 2. Critical Situations: • In critical situations where immediate action is necessary, the test with the highest yield (likelihood of providing a clear diagnosis or treatment direction) may be chosen, even if it carries some risks. 3. Non-Critical Situations: • When time allows and the patient’s condition allows for it, less risky or lower yield tests may be conducted first to gather preliminary information.
In what order should perform tests for patients?
Order of Testing:
1. From Cheap to Costly: • Starting with less expensive tests can be economical and practical, especially when resources are limited. 2. From Less to More Risky: • Conducting less invasive or risky tests before more invasive ones minimizes potential harm to the patient. 3. From Simple to Complex: • Beginning with simpler tests helps establish a baseline understanding before proceeding to more complex diagnostic procedures.
The above order is Not always practical.
One or more objectives may be sacrificed for speed, convenience, accuracy, a waiting list for procedures, time needed to await the results, and the condition of the patient.
Sometimes it may be best to get the costly test done first; it may solve the problem quickly and save money in the long run.
Practical Considerations:
• Speed and Convenience: Sometimes, tests are prioritized based on how quickly results are needed or how convenient they are to perform. • Accuracy: The reliability and accuracy of each test are crucial considerations in determining their order. • Cost-effectiveness: Occasionally, conducting a more costly test upfront may be justified if it can quickly resolve the diagnostic uncertainty and potentially save costs in the long run.
State two sources of variations in test results
SOURCES OF VARIATION IN TEST RESULTS
1 Analytical factors These cause errors in measure-ment.
2 Biological and pathological factors Both these sets of factors affect the concentrations of analytes in blood, urine and other fluids sent for analysis.
State four indicators of test reliability
Which of the indicators reflect how well the test method performs day to day in a laboratory?(they are two )
Which of the indicators deal with how well the test is able to distinguish disease from absence of disease?(they are two)
What are the indicators of test reliability?
• Accuracy, Precision, Specificity and Sensitivity
• Accuracy and precision reflect how well the test method performs day to day in a laboratory.
• Sensitivity and specificity deal with how well the test is able to distinguish disease from absence of disease.
• These are effectively analytical sources of variation.
What is precision of a test
What is accuracy of a test
There’s a picture explaining this further in the chem path slides
MCQ 1
A new assay for measuring glucose levels in blood is tested by running the same sample 10 times. The results are consistently between 100-105 mg/dL, but the reference method shows the true glucose level is 90 mg/dL. How would you describe the performance of this assay?
A) Precise but not accurate
B) Accurate but not precise
C) Both precise and accurate
D) Neither precise nor accurate
A laboratory uses two different assays to measure serum cholesterol. Assay A shows results consistently around 200 mg/dL for a sample, while Assay B shows results around 190 mg/dL for the same sample. The reference method indicates the true value is 195 mg/dL. Which statement is true?
A) Both assays are precise and accurate
B) Assay A is precise but not accurate; Assay B is accurate but not precise
C) Both assays are precise but not accurate
D) Both assays are accurate but not precise
A laboratory reports that a new enzyme assay for measuring liver function yields results that are highly variable with different runs but consistently average at the expected true value. How would you describe this assay?
A) Precise and accurate
B) Precise but not accurate
C) Accurate but not precise
D) Neither precise nor accurate
A new biochemical assay for measuring serum creatinine is evaluated. The assay shows the following results for a single sample across multiple runs: 85, 86, 87, 85, and 86 µmol/L. However, the reference method indicates the true creatinine level is 80 µmol/L. What is the most accurate description of the assay’s performance?
A) Precise but not accurate
B) Accurate but not precise
C) Both precise and accurate
D) Neither precise nor accurate
In a comparative study, a laboratory finds that a new test for measuring serum albumin has results within 1% of the reference method’s values for all tested samples, but the variability between test results is quite high (coefficient of variation is 10%). What does this suggest about the new test?
A) Precise and accurate
B) Precise but not accurate
C) Accurate but not precise
D) Neither precise nor accurate
PRECISION AND ACCURACY IN BIOCHEMICAL TESTS
• Precision:The amount of variation in results after measuring the same sample repeatedly. So four test results can be wrong in the same area but will be said to be precise just not accurate. They are precise because they are in the same area.
• A test method is said to be precise when repeated analyses on the same sample give similar results.
• Accuracy:How close the result Is to the “true” value as determined by a reference method. Four test results are all correct but are in different areas.
1.A
2.C
3.C
4.A
5.C
Although a test that is 100% accurate and 100% precise is ideal, in practice, test methodology, instrumentation, and laboratory operations all contribute to small but measurable variations in results.
True or false
True
BIOLOGICAL CAUSES OF VARIATION
• As well as analytical variation, test results also show biological variation in both health and disease.
• Key questions are:
• How do results vary in health?
• How do results vary in disease?
Explain how results vary in disease
Explain how results vary in health
How do results vary in health?
• The concentrations of all analytes in blood vary with time due to diverse physiological factors WITHIN the individual.
• There are also differences BETWEEN individuals.
The variability in analyte concentrations in blood is influenced by several factors, which can be categorized into within-individual and between-individual differences:
Within individuals:
Physiological Factors:
- Diurnal Variation: Many analytes fluctuate throughout the day. For example, cortisol levels are typically higher in the morning and lower in the evening.
- Food Intake: Levels of glucose, lipids, and other nutrients can change based on recent food consumption.
- Physical Activity: Exercise can affect analyte levels such as lactate and electrolytes.
- Hydration Status: Dehydration or overhydration can impact concentrations of substances like sodium and potassium.
- Stress: Acute stress can alter levels of hormones like adrenaline and cortisol.
- Medications: Timing and type of medication can influence analyte levels, such as blood glucose levels in diabetic patients taking insulin.
Between individuals:
Genetic Factors:
- Genetic Variants: Different individuals may have genetic variations affecting enzyme activity, receptor function, or metabolic pathways, leading to variations in analyte levels.
Environmental and Lifestyle Factors:
- Diet: Dietary habits, such as intake of vitamins, minerals, and other nutrients, can influence analyte levels.
- Lifestyle: Factors such as smoking, alcohol consumption, and overall physical fitness impact various biomarkers.
- Health Status: Chronic conditions like diabetes, hypertension, or liver disease can alter baseline analyte levels.
Demographic Factors:
- Age: Certain analytes change with age. For instance, hormone levels or renal function markers may vary across different age groups.
- Sex: Hormonal differences between genders can affect analyte levels, such as testosterone and estrogen levels.
Understanding these variations is crucial for accurate interpretation of test results. Factors such as timing of the sample collection, patient preparation, and individual health status should be considered to account for variability and ensure reliable results.
B How do results vary in disease?
• Biochemical test results do not exist in isolation.
• For example, in a patient with severe abdominal pain, tenderness and rigidity, there may be several differential diagnoses to consider - including, for example,
• acute pancreatitis
• perforated peptic ulcer and
• acute cholecystitis.
In the context of disease, biochemical test results can vary due to the presence of multiple underlying conditions, and their interpretation must consider the broader clinical picture. Here’s how results can vary based on different diseases and why it’s important to consider differential diagnoses:
Acute Pancreatitis:
- Biochemical Markers: Elevated serum amylase and lipase are commonly associated with acute pancreatitis. However, levels can also be influenced by the severity and timing of the onset.
- Other Considerations: The severity of the disease can affect the degree of enzyme elevation, and overlapping conditions like chronic alcoholism or gallstones may further complicate the results.
Perforated Peptic Ulcer:
- Biochemical Markers: Perforation of a peptic ulcer often leads to elevated white blood cell counts (leukocytosis) due to inflammation and possible sepsis. Serum electrolytes may also be affected if there is significant gastrointestinal fluid loss.
- Other Considerations: The presence of free air in the abdominal cavity and subsequent infection can influence various biomarkers, and test results must be interpreted in the context of imaging findings and clinical symptoms.
Acute Cholecystitis:
- Biochemical Markers: Elevated serum bilirubin, alkaline phosphatase, and transaminases (AST, ALT) can be indicative of acute cholecystitis. Inflammation of the gallbladder often affects these liver enzymes.
- Other Considerations: If there is obstruction of the bile duct, additional tests like ultrasound or HIDA scan may be necessary to confirm the diagnosis and differentiate it from other conditions such as pancreatitis or liver disease.
- Complex Clinical Picture: When a patient presents with symptoms like severe abdominal pain, biochemical tests alone are not sufficient. The clinical presentation and other diagnostic tools (e.g., imaging studies, endoscopy) play a crucial role in differentiating between conditions.
- Test Results Integration: Test results must be integrated with clinical symptoms and history. For example, elevated lipase in the context of abdominal pain might suggest pancreatitis, but similar results could occur with other conditions affecting the abdominal organs.
A patient presents with severe abdominal pain and elevated serum amylase and lipase. The differential diagnosis includes acute pancreatitis and perforated peptic ulcer. What additional information would be most crucial in distinguishing between these two conditions?
A) Patient’s age
B) Serum cholesterol levels
C) Presence of free air on imaging
D) Serum bilirubin levels
Answer: C) Presence of free air on imaging
Explanation: The presence of free air on imaging is indicative of perforated peptic ulcer, which can help differentiate it from acute pancreatitis, which would not typically present with free air.
A patient with suspected acute cholecystitis has elevated serum bilirubin and alkaline phosphatase levels. Which other test result is likely to be elevated if the patient has acute cholecystitis?
A) Serum amylase
B) Serum lipase
C) Serum AST
D) Serum sodium
Answer: C) Serum AST
Explanation: Elevated serum AST (aspartate aminotransferase) is commonly associated with liver and gallbladder issues, including acute cholecystitis, alongside elevated bilirubin and alkaline phosphatase.
In a case of severe abdominal pain with elevated white blood cell count (WBC) and normal serum amylase and lipase, which condition is most likely if the patient also exhibits signs of gastrointestinal fluid loss?
A) Acute pancreatitis
B) Acute cholecystitis
C) Perforated peptic ulcer
D) Hepatitis
Answer: C) Perforated peptic ulcer
Explanation: Perforated peptic ulcer often presents with elevated WBC count due to inflammation and potential infection, and gastrointestinal fluid loss can affect the patient’s overall clinical status.
These MCQs test your ability to interpret biochemical test results in the context of differential diagnoses, integrating clinical symptoms with laboratory findings.
BIOLOGICAL CAUSES OF VARIATION
• As well as analytical variation, test results also show biological variation in both health and disease.
• Key questions are:
• How do results vary in health?
• How do results vary in disease?
Explain how results vary in disease
Explain how results vary in health
How do results vary in health?
• The concentrations of all analytes in blood vary with time due to diverse physiological factors WITHIN the individual.
• There are also differences BETWEEN individuals.
B How do results vary in disease?
• Biochemical test results do not exist in isolation.
• For example, in a patient with severe abdominal pain, tenderness and rigidity, there may be several differential diagnoses to consider - including, for example,
• acute pancreatitis
• perforated peptic ulcer and
• acute cholecystitis.
State five causes of within individual variations under biological causes of variations
So, “within-individual” is like how you change over time, and “between-individual” is how you’re different from other people!
Within-individual variation
• The following may be important causes of within individual variation:
DIET: Variations in diet can affect the results of many tests, including serum triglyceride
• TIME OF DAY: Several plasma constituents show diurnal variation (variation with the time of day), or a sleep/wake cycle. Example is cortisol
• POSTURE: Proteins and all protein-bound constituents of plasma show significant differences in concentration between blood collected from upright individuals and blood from recumbent individuals. People in the upright position generally have lower protein concentrations compared to those in the recumbent (lying down) position. This is due to the effects of gravity on the distribution of fluids in the body:
• Upright Position: In this position, blood is pooled in the lower extremities, and there is a relative decrease in the concentration of proteins in the blood plasma due to increased fluid shift into the lower parts of the body. • Recumbent Position: When lying down, the blood is more evenly distributed throughout the body, and the concentration of plasma proteins tends to be higher as there is less pooling in the lower extremities.
Within-individual variation cont’d
• MUSCULAR EXERCISE: Recent exercise, especially if vigorous or unaccustomed, may increase serum creatine kinase (CK) activity in blood [lactate], and lower blood [pyruvate].
• MENSTRUAL CYCLE: Several substances show variation with the phase of the cycle. Examples include serum [iron], and the serum
concentrations of the pituitary gonadotrophins
• DRUGS: These can have marked effects on chemical results.
Certainly! Here are five challenging MCQs focusing on within-individual variation and its impact on biochemical test results:
A study examines the effect of posture on serum albumin levels. Researchers find that serum albumin concentrations are significantly higher when blood is drawn from patients in an upright position compared to when drawn in a recumbent position. What is the most likely reason for this variation?
A) Increased protein synthesis during upright posture
B) Redistribution of fluids from plasma to interstitial spaces when upright
C) Enhanced renal excretion of albumin when lying down
D) Altered hepatic production of albumin in response to posture
Answer: B) Redistribution of fluids from plasma to interstitial spaces when upright
Explanation: Upright posture leads to fluid redistribution from the plasma to the interstitial spaces, which increases serum albumin concentrations compared to when lying down.
A patient undergoes routine blood testing for serum cortisol levels. The results show elevated cortisol levels in the early morning but normal levels later in the day. Which physiological factor is most likely responsible for this variation?
A) Dietary intake
B) Time of day
C) Physical exercise
D) Posture
Answer: B) Time of day
Explanation: Cortisol follows a diurnal rhythm, with higher levels in the early morning and lower levels throughout the day, reflecting the natural sleep/wake cycle.
A patient with a history of vigorous exercise shows elevated serum creatine kinase (CK) levels. How does recent muscular exercise primarily affect these CK levels?
A) Increases CK levels due to muscle damage and increased release of CK into the bloodstream
B) Decreases CK levels due to enhanced renal clearance of CK
C) Increases CK levels due to dietary influences
D) Decreases CK levels due to alteration in muscle metabolism
Answer: A) Increases CK levels due to muscle damage and increased release of CK into the bloodstream
Explanation: Vigorous or unaccustomed exercise can lead to muscle damage, resulting in increased serum CK levels as CK is released from damaged muscle tissues.
A study investigates the effects of the menstrual cycle on serum iron levels. Researchers find that serum iron levels are lower during the menstrual phase compared to other phases. What is the most likely reason for this variation?
A) Increased gastrointestinal absorption of iron during menstruation
B) Decreased total blood volume during menstruation
C) Altered hepatic iron storage during menstruation
D) Increased loss of iron through menstrual bleeding
Answer: D) Increased loss of iron through menstrual bleeding
Explanation: During menstruation, there is increased loss of iron due to menstrual bleeding, which can lower serum iron levels.
A patient is taking a medication that significantly affects their serum triglyceride levels. What is the most likely effect of this medication on the biochemical test results?
A) Consistent triglyceride levels regardless of medication use
B) Marked increase or decrease in triglyceride levels depending on the medication’s action
C) Altered protein-bound triglyceride concentrations without affecting total triglycerides
D) Reduced variation in triglyceride levels due to stabilized metabolic processes
Answer: B) Marked increase or decrease in triglyceride levels depending on the medication’s action
Explanation: Certain medications can significantly alter triglyceride levels, leading to marked increases or decreases depending on the medication’s effects on lipid metabolism.
These questions are designed to test deep understanding of how various factors can influence biochemical test results, especially focusing on within-individual variations.
State three causes of between individual variations under biological causes of variation
So, “within-individual” is like how you change over time, and “between-individual” is how you’re different from other people!
Between individual variation
• Differences between individuals can affect the concentrations of analytes in the blood. The following are the main examples:
• AGE: Examples include serum [phosphate] and alkaline phosphatase (ALP) activity
• SEX: Examples include serum creatinine, iron, uric acid and urea concentrations
• RACE: Racial differences have been described for serum [cholesterol] and [protein].
It may be difficult to distinguish racial from environmental factors, such as diet
Here’s a summary:
- Serum Phosphate: Higher in children/adolescents due to bone growth; lower in adults; may increase in the elderly due to reduced kidney function.
- Alkaline Phosphatase (ALP): Higher in children/adolescents due to active bone growth; lower in adults; may rise again in the elderly due to bone conditions.
- Iron: Higher in males (no menstrual blood loss); lower in females (due to menstruation and pregnancy).
- Creatinine: Higher in males due to greater muscle mass; lower in females.
- Uric Acid: Higher in males due to purine metabolism; lower in pre-menopausal females (estrogen increases uric acid excretion).
- Urea: Slightly higher in males due to higher protein intake and muscle mass; slightly lower in females.
Age and sex are important factors to consider when interpreting biochemical test results, as they significantly influence normal values.
