WorksheetsClinical Biochemistry MCQs (Extraction)
Total questions: 79
Worksheet time: 40mins
Clinical biochemistry primarily involves the analysis of:
Only urine
Body fluids and tissues
Radiographic images
Genetic sequences
A major purpose of clinical biochemistry is NOT:
Disease diagnosis
Monitoring treatment
Screening for disease
Performing surgery
Which is a core feature of specialized tests?
Available in all labs
Often referred to larger labs
Performed only at bedside
Never urgent
Emergency laboratory tests are mainly intended to:
Reduce costs
Provide rapid results for urgent situations
Replace routine tests
Eliminate the need for clinicians
Which sample contains RBCs, WBCs, and platelets in suspension?
Serum
Plasma
Whole blood
Distilled water
Whole blood tests commonly include:
Serum electrolytes
CBC, ESR, blood gases
Coagulation profile only
Thyroid function tests
Serum is obtained by:
Adding anticoagulant then centrifuging
Allowing blood to clot then centrifuging
Freezing then thawing blood
Filtering whole blood
Plasma is obtained by:
Clotting blood then centrifugation
Using anticoagulant then centrifugation
Evaporation of serum
Using serum separator gels only
Compared to plasma, serum lacks:
Water
Glucose
Clotting factors including fibrinogen
Electrolytes
Serum is preferred for many chemistry tests because:
It has higher RBC content
Clotting factors may interfere with tests
It is easier to freeze
It has more anticoagulant
Plasma is commonly used for:
STAT chemistry and coagulation studies
Histology
Bacterial culture
Imaging
“Serum = Plasma – _____”
Water
Cells
Clotting factors
Proteins
A major pre-analytical error that causes falsely high potassium is:
Fasting too long
Hemolysis during sampling
Using serum instead of plasma
Centrifuging too early
Prolonged venous stasis during venipuncture can cause:
Dilution of analytes
Concentration of proteins and protein-bound analytes
Hemodilution by saline
Increased oxygenation
Insufficient specimen volume primarily risks:
Bacterial contamination
Inability to perform all requested tests
Hyperglycemia
Hypokalemia
Storing whole blood overnight at room temperature can falsely increase:
Sodium only
Potassium, phosphate, and LDH
Calcium and chloride
Bicarbonate
Glucose samples should be collected in tubes containing:
Heparin
EDTA
Fluoride
Citrate only
Using an EDTA tube for chemistry calcium testing may cause:
Falsely high calcium
Falsely low calcium
No change
Hemolysis only
A red appearance of serum/plasma indicates:
Icterus
Hemolysis
Lipemia
Turbidity from proteins
Milky serum suggests:
Icterus
Lipemia
Hemolysis
Hyperbilirubinemia
Yellow to brownish serum is described as:
Lipemic
Hemolyzed
Icteric
Turbid
Biochemistry results are often reported in:
mol/L, mg/dL, or µg/mL
meters/second
mmHg
dB
Analytical variation refers to:
Physiological fluctuations in the patient
Performance and precision of the method
Diet-related changes
Circadian rhythms
Biological variation refers to:
Instrument drift
Reagent lot changes
Natural physiological fluctuations over time
Calculation errors
Concentration depends on:
Solute only
Solvent only
Both solute amount and solvent volume
Temperature only
Precision is best defined as:
Closeness to the true value
Reproducibility of repeated measurements
Average of values
Range of reference interval
Accuracy is best defined as:
Reproducibility
Closeness to the true value
Least significant digit
Linearity
The ideal analytical method aims for:
High precision and low accuracy
Low precision and high accuracy
High precision and high accuracy
Moderate precision only
Sensitivity is the ability of a test to:
Rule in disease when positive
Rule out disease when negative
Predict treatment response
Measure biological variation
Specificity is the ability of a test to:
Rule in disease when positive
Rule out disease when negative
Reduce pre-analytical errors
Determine precision
A highly sensitive test is valuable for:
Confirming disease
Screening and ruling out disease
Monitoring therapy only
Pharmacokinetics only
A highly specific test is valuable for:
Screening low-risk populations
Confirming a diagnosis (rule in)
Measuring precision
Reducing hemolysis
Reference intervals can differ by:
Sex and age only
Sex, age, diet, collection timing
Lab temperature only
Instrument brand only
Stress and anxiety may elevate:
Calcium
Cortisol and catecholamines
Bilirubin
Sodium
Patient position at collection can influence:
None of the analytes
Only glucose
Several analytes due to fluid shifts
Imaging outcomes
Strenuous exercise can:
Decrease all enzymes
Increase some muscle enzymes
Eliminate biological variation
Replace fasting
Pregnancy typically:
Has no effect on biochemistry
Alters reference intervals for various analytes
Lowers all enzymes
Eliminates circadian rhythm
The menstrual cycle:
Does not affect lab values
Can cause hormonal fluctuations affecting results
Only affects CBC
Only affects bilirubin
Medical and drug history:
Is irrelevant to results
Can significantly affect biochemical values
Only affects whole blood tests
Only affects serum tests
A spectrophotometer is used in:
Colorimetric and kinetic methods
Microscopy only
Chromatography only
Imaging
In basic colorimetry, the measured signal is related to:
Sound intensity
Absorbance of light by the sample
Electrical resistance
Blood pressure
Kinetic methods determine concentration by:
Endpoint color only
Rate of change of absorbance over time
Sample pH only
Electrical conductivity
A hemolyzed sample most significantly affects:
Sodium
Potassium, LDH, and AST
Chloride
Bicarbonate
Lipemia commonly occurs due to:
Fasting
Recent eating or rare hereditary causes
Sample heating
Anticoagulant use
Icterus in serum commonly indicates:
Hyperlipidemia only
Liver disease or excessive RBC breakdown
Dehydration
Renal failure
Prolonged stasis primarily affects:
Free water balance only
Protein-bound analytes like calcium and thyroxine
Hemoglobin oxygen saturation
Blood pH
The most common laboratory test overall is:
Thyroid panel
Complete blood count (CBC)
Troponin
D-dimer
For coagulation studies, the preferred specimen is:
Serum
Plasma with appropriate anticoagulant
Whole blood without anticoagulant
Dried blood spot
The component unnecessary in serum collection is:
Plain tube (no anticoagulant)
Allowing clot formation
Anticoagulant
Centrifugation
Explain the main roles of clinical biochemistry in patient care.
Supporting diagnosis by identifying biochemical abnormalities
Monitoring treatment by tracking biomarker changes
Screening populations for disease risk
Performing imaging procedures to localize pathology
Recording detailed patient histories for clinicians
Distinguish between core, specialized, and emergency laboratory tests with examples. Which option correctly describes all three categories with appropriate examples?
Core tests are highly complex and referred out; specialized tests are routine electrolytes and glucose; emergency tests are annual wellness panels.
Core tests are routine such as electrolytes and glucose; specialized tests are complex and may require referral such as specialized hormones or genetic enzyme assays; emergency tests provide rapid results for urgent care such as troponin, arterial blood gases, and electrolytes in critical care.
Core tests are only point-of-care; specialized tests are only microbiology cultures; emergency tests are only imaging requests.
Core tests, specialized tests, and emergency tests are synonymous categories used interchangeably in chemistry.
Compare whole blood, serum, and plasma in terms of composition and typical uses. Which statement is correct?
Whole blood lacks cells and is used only for serology; serum contains anticoagulants and is used for coagulation studies; plasma is the fluid remaining after clotting and is used for CBC.
Whole blood contains cells and plasma and is used for CBC, ESR, and blood gases; serum is plasma minus clotting factors after clotting and is used for chemistry and serology; plasma is obtained using anticoagulants, retains clotting factors, and is used for STAT tests and coagulation studies.
Whole blood is the same as plasma; serum is used only for microbiology; plasma is created by allowing blood to clot and removing cells.
Describe the process of obtaining serum and why it may be preferred for many chemistry tests. Which option best reflects the correct steps and rationale?
Collect blood in an anticoagulated tube and immediately analyze without separation to avoid protein loss.
Collect blood in a plain tube, allow it to clot, and centrifuge to separate the clear supernatant; serum is preferred because clotting removes factors like fibrinogen that might interfere.
Collect blood in a fluoride/oxalate tube and freeze before spinning; serum is preferred because it retains clotting factors.
Describe how plasma is obtained and list two common clinical scenarios where plasma is essential. Which option is accurate?
Collect blood in a plain tube and allow it to clot; plasma is essential for serology and blood culture.
Collect blood into an anticoagulant such as heparin or citrate, then centrifuge; plasma is essential for coagulation testing and for urgent/STAT chemistry where rapid processing is needed.
Collect blood into a serum separator tube and let it stand overnight; plasma is essential for lipid panels and thyroid tests.
Outline pre-analytical sampling errors and their effects on results. Select all that are typical errors described and their characteristic impacts.
Difficult venipuncture causing hemolysis, leading to increased K+, LDH, and AST.
Prolonged tourniquet stasis concentrating proteins and protein-bound analytes such as Ca and T4.
Incorrect storage overnight causing elevated K+, phosphate, and LDH from cell leakage.
Using the recommended container for each test and prompt processing, which prevents changes in analytes.
Collecting glucose without fluoride, allowing glycolysis and decreased glucose.
Explain hemolysis, lipemia, and icterus and their typical laboratory impacts. Which interferences are most associated with optical interference in chemistry assays?
Hemolysis from RBC rupture releasing hemoglobin
Lipemia from high triglycerides or a recent meal
Icterus from high bilirubin due to liver disease or hemolysis
Leukocytosis from infection
Define analytical and biological variation with clinical examples. Which statement best distinguishes them?
Analytical variation arises from physiological changes such as diurnal cortisol; biological variation arises from instrument performance across runs.
Analytical variation relates to instrument, reagent, or method performance such as imprecision across runs; biological variation comes from physiological changes such as diurnal cortisol, postprandial glucose, or day-to-day creatinine variation.
Analytical and biological variation are identical concepts and interchangeable in clinical chemistry.
Differentiate accuracy and precision and explain why both are important. Which option is correct?
Precision is closeness to the true value; accuracy is reproducibility; only accuracy matters clinically.
Precision is reproducibility and accuracy is closeness to the true value; both are important to avoid misleading clinical decisions.
Precision and accuracy refer only to calibration frequency and are not relevant to clinical decisions.
Using a sugar solution example, explain how concentration can change without altering the solute amount. Which statement best illustrates this principle?
Reducing the volume of solvent by evaporation increases concentration; increasing solvent dilutes the solution, showing concentration depends on both solute and solvent.
Concentration is fixed once the solute is added and does not change with solvent volume.
Adding more solute decreases concentration if the solvent volume is constant.
Define sensitivity and specificity, and state when each is most clinically useful. Which pairing is correct?
Sensitivity identifies those without disease and is useful for confirming a diagnosis; specificity identifies those with disease and is useful for screening.
Sensitivity is the ability to detect disease with few false negatives and is useful for ruling out and screening; specificity is the ability to identify those without disease with few false positives and is useful for confirming a diagnosis (rule in).
Sensitivity and specificity are interchangeable metrics that both rule in disease.
Provide an example of pairing a screening test with a confirmatory test based on sensitivity and specificity principles. Which option matches the described approach?
Use a highly sensitive D-dimer to screen for thromboembolism; if positive, follow with a specific confirmatory test such as imaging or specific assays to rule in disease.
Begin with a highly specific imaging study for all patients, then follow with a sensitive screening test to rule out disease.
Use two screening tests in sequence without confirmatory testing to save time.
Identify physiological factors that can alter reference intervals. Select all that apply.
Sex differences such as higher creatinine in men
Age such as higher bilirubin in neonates
Timing and posture such as morning cortisol or standing increasing protein concentration
Routine use of quality control materials in the analyzer
Medications such as steroids increasing glucose
Explain how prolonged venous stasis alters laboratory results and name analytes most affected. Which option is correct?
Stasis dilutes intravascular proteins, lowering protein-bound analytes such as calcium and T4.
Stasis allows plasma water to filter into tissues, concentrating intravascular proteins and protein-bound analytes; calcium and thyroxine (T4) notably increase falsely.
Stasis has no significant effect on protein-bound analytes.
Discuss appropriate tube types for common tests and the consequences of errors. Which option best matches correct use and typical errors?
Use EDTA for chemistry panels to avoid chelation; avoid fluoride for glucose to prevent falsely high glucose; use citrate for CBC.
Use serum separator tubes for chemistry, fluoride/oxalate for glucose, EDTA for CBC, and citrate for coagulation; using EDTA for chemistry can chelate calcium causing falsely low Ca and add potassium causing falsely high K+; lacking fluoride in glucose samples allows glycolysis causing falsely low glucose.
Use plain tubes for all tests to standardize processing; tube choice does not affect results.
Describe storage-related artifacts in blood samples and how to prevent them.
Room-temperature storage causes cellular leakage (increased K+, phosphate, LDH); prevent with prompt centrifugation, correct temperature, timely analysis, and preservatives when indicated.
Room-temperature storage stabilizes all electrolytes; prevent issues by delaying centrifugation until the next day.
Cold storage always increases hemolysis; prevent by keeping samples at body temperature and avoiding preservatives.
Artifacts arise only from transport vibration; prevent by vigorous shaking and prolonged standing.
Outline the components of a basic colorimeter/spectrophotometer and their functions.
Light source, monochromator or filter to select wavelength, cuvette to hold sample, detector to measure transmitted/absorbed light, and readout; use calibration standards for accuracy.
Light source only, because detectors and cuvettes are optional in most instruments.
Two detectors without a light source, with wavelength selection handled by the sample matrix.
Cuvette and readout alone; wavelength is chosen by room lighting.
Compare endpoint colorimetric and kinetic assays with an example of each.
Endpoint measures final absorbance after reaction completion (e.g., total protein by biuret); kinetic measures rate of change over time (e.g., ALT or AST).
Endpoint measures the fastest rate of change (e.g., CK); kinetic records only the final color after stopping the reaction.
Both endpoint and kinetic assays require no timing and are interchangeable for enzymes.
Endpoint reports activity per minute; kinetic reports concentration after equilibrium.
Explain how lipemia interferes with spectrophotometric assays and methods to mitigate it.
Turbidity from lipemia scatters light, altering apparent absorbance; mitigate by ultracentrifugation or clearing agents, serum blanking, or alternative wavelengths/methods.
Lipemia increases only red fluorescence and needs no correction.
Lipemia chelates calcium, so use EDTA to clear it in spectrophotometry.
Lipemia improves linearity; mitigate by diluting every sample 1:100.
Provide a stepwise approach to interpreting an abnormal lab result in context.
Confirm patient identity and timing; assess pre-analytical issues; review reference intervals (age/sex); check medications and clinical context; repeat if needed; correlate with other tests.
Assume result is correct, call the patient immediately, and treat empirically without repeat testing.
Average the current result with prior values to remove error and avoid repeats.
Ignore reference intervals and focus on instrument flags only.
Describe how circadian rhythms influence sample timing recommendations.
Some analytes vary by time of day (e.g., morning cortisol peak); standardizing collection time (e.g., 8 AM cortisol) improves comparability.
Circadian rhythms affect only heart rate, not laboratory analytes.
Evening sampling is always superior for all endocrine tests.
Random timing reduces variability more than standardizing time.
Discuss the impact of strenuous exercise on laboratory enzymes and electrolytes.
Exercise can raise CK, AST, and LDH from muscle and cause transient shifts in potassium and lactate; results should consider recent activity.
Exercise lowers all enzyme levels and normalizes electrolytes within minutes.
Exercise only affects cholesterol; enzymes and electrolytes are unchanged.
Exercise effects are negligible and do not require documentation.
Explain why pregnancy requires adjusted reference intervals with two examples.
Physiologic plasma volume expansion and hormonal changes alter analytes; examples include decreased albumin (dilutional) and increased alkaline phosphatase (placental isoenzyme).
Pregnancy uniformly increases all proteins and decreases all enzymes; no examples are needed.
Pregnancy has no effect on laboratory values if fasting is observed.
Changes occur only in hematology, not chemistry.
Provide an algorithm to handle a hemolyzed potassium result.
Inspect for hemolysis or review hemolysis index; if hemolyzed and K+ is high, recollect with careful phlebotomy; if the repeat is high without hemolysis, evaluate for true hyperkalemia clinically.
Always report the initial value and avoid repeat collection to prevent delay.
Dilute the sample until potassium normalizes, then release the result.
Treat the patient with calcium immediately without verifying hemolysis.
Describe the role of fluoride in glucose tubes and consequences of omission.
Fluoride inhibits glycolysis in red cells, stabilizing glucose; without it, glucose falls over time causing falsely low results, especially with delayed processing.
Fluoride enhances enzyme activity so glucose rises if omitted.
Fluoride prevents hemolysis only; glucose is unaffected by omission.
Omitting fluoride causes falsely high glucose due to preservative contamination.
Explain how patient position affects analytes and standardization recommendations.
Standing causes hemoconcentration with higher proteins and calcium; standardize to a seated/rested position before draw and document if deviating.
Supine posture always lowers hemoglobin to zero; no standardization is necessary.
Patient position changes only hematocrit and not chemistry analytes; any position is acceptable.
Walking to the lab eliminates posture effects, so timing is irrelevant.
Discuss the relationship between analytical precision and clinical decision limits.
Greater imprecision widens uncertainty near cutoffs, increasing misclassification; improved precision reduces error near decision limits.
Imprecision narrows confidence around cutoffs, making classification easier.
Decision limits are unaffected by method precision.
Better precision increases false positives near thresholds.
Define reference interval and how it is established.
It is the range for a defined healthy population (often central 95%); established by sampling an appropriate reference group, partitioning by factors like sex/age, and determining the 2.5th–97.5th percentiles.
It is the mean of hospital inpatients; established by averaging all results from one day.
It is the widest possible range covering 100% of values; established by manufacturer only.
It is a physician-selected cutoff unrelated to population sampling.
Describe quality control approaches to ensure accuracy and precision in a clinical lab.
Use internal QC with control materials and Levey–Jennings charts applying Westgard rules; participate in external proficiency testing; maintain calibration, instruments, and staff competency.
Rely solely on manufacturer brochures without running controls.
Run controls only when results look abnormal; charts are optional.
Use external proficiency testing alone and disable internal QC to save reagents.
Summarize best practices for minimizing pre-analytical errors in phlebotomy.
Ensure correct patient identification, proper tubes and order of draw, avoid prolonged tourniquet time, gentle mixing when required, adequate volume, prompt transport and processing, proper storage, document posture/timing/diet/medications, and minimize hemolysis with correct needle size and technique.
Focus only on rapid collection; labeling and order of draw are optional.
Freeze all samples immediately to prevent any error regardless of test.
Use the smallest possible needle for all draws to standardize hemolysis.
