Clinical Biochemistry Basics

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Questions and Answers

What is a primary reason for not using tissue samples in medical analysis?

Tissue samples provide more accurate results than blood.

The process is expensive and complex. (correct)

Tissue samples are easier to obtain than blood samples.

Tissue sample collection is non-invasive.

Which biological sample is most frequently used for medical purposes?

Cerebrospinal fluid

Urine

Blood (correct)

Breast milk

What is a key characteristic of blood that makes it a valuable biological sample?

It contains no cellular components.

It cannot transport hormones.

It contacts almost all body tissues. (correct)

It is only produced in the lungs.

Which of the following components is NOT typically found in blood?

Stool Signup and view all the answers

What occurs during physiological cell death that affects blood composition?

There is a leakage of molecules into the bloodstream. Signup and view all the answers

Which organ does NOT contribute actively to the composition of blood?

Spleen Signup and view all the answers

What does an increase in the amount of a substance in blood typically indicate?

Tissue damage or disease. Signup and view all the answers

Which of the following is a disadvantage of using blood samples?

Blood collection is typically invasive. Signup and view all the answers

What is the primary focus of clinical biochemistry?

To interpret laboratory data for disease diagnosis Signup and view all the answers

What glucose level indicates the presence of diabetes mellitus?

126 mg/dL or above Signup and view all the answers

What is a normal phenylalanine concentration in newborns?

0.5 mg/dL to 1 mg/dL Signup and view all the answers

What condition is indicated by an HbA1c level greater than 9.0%?

Poor control of diabetes Signup and view all the answers

Which biological specimen is optimal for measuring illness-associated chemicals?

Tissue samples Signup and view all the answers

Which of the following describes the analytical aspect of clinical biochemistry?

Determination of chemical levels in biological fluids Signup and view all the answers

What is the main role of the interpretative science in clinical biochemistry?

Using test results for disease diagnosis and monitoring Signup and view all the answers

What factors could poor control of diabetes lead to?

Increased risk of renal failure and blindness Signup and view all the answers

What factor typically causes urine to have a lighter color?

Increased water intake Signup and view all the answers

What is the typical pH range of normal urine?

4.6 – 8.0 Signup and view all the answers

Which characteristic of urine is primarily affected by the presence of suspended particles?

Turbidity Signup and view all the answers

What does a dark color in urine typically indicate?

Low hydration Signup and view all the answers

What is the density range for normal urine?

1.001 to 1.035 Signup and view all the answers

What might an increase in urinary turbidity indicate?

Presence of suspended particles Signup and view all the answers

Which dietary factor is likely to make urine more acidic?

High protein intake Signup and view all the answers

How is the turbidity of urine typically reported?

As clear, slightly cloudy, cloudy, opaque, or flocculent Signup and view all the answers

Which of the following is NOT typically measured using whole blood?

Fibrinogen Signup and view all the answers

What is the primary purpose of sodium fluoride in blood collection tubes?

Inhibits glycolysis to preserve glucose levels Signup and view all the answers

Which components are included in a typical Liver Panel?

AST, ALT, ALP, Bilirubin Signup and view all the answers

Which anticoagulant is commonly used for immediate platelet count assays?

EDTA Signup and view all the answers

What is a characteristic of urine as a diagnostic specimen?

Provides insights into both physical and chemical processes in the body Signup and view all the answers

Which of the following components is generally NOT part of a Renal Panel?

TSH Signup and view all the answers

What is the significance of a marked elevation of ALT and AST levels in acute hepatitis?

It suggests liver cell damage. Signup and view all the answers

What can be said about the composition of laboratory test panels?

It may vary according to laboratory capacity and practice. Signup and view all the answers

Which of the following statements is true regarding alkaline phosphatase (ALP) levels in adults?

Normal serum ALP concentration ranges from 37 to 116 U/L. Signup and view all the answers

Which of the following is primarily associated with the measurement of glucose levels in blood?

Blood tubes containing sodium fluoride Signup and view all the answers

How can placental alkaline phosphatase be distinguished from liver and bone isoenzymes?

Placental ALP is more stable at elevated temperatures. Signup and view all the answers

What is the role of total serum alkaline phosphatase activity in children?

It serves as a marker for bone formation. Signup and view all the answers

What is the typical serum concentration of ALP in a pregnant woman?

Around 2817 U/L. Signup and view all the answers

What does a decrease in levels of proteins secreted into blood imply?

Possible tissue damage or disease. Signup and view all the answers

What is the procedure to understand the effect of heat on ALP activity?

Heat serum sample at 56 °C for 15 minutes. Signup and view all the answers

What is a characteristic of the ALP isoenzymes synthesized by different tissues?

They can have different physical properties. Signup and view all the answers

What urine pH value corresponds to omnivores in the study?

5.74 Signup and view all the answers

Which condition may be indicated by lower urine creatinine levels?

Renal disease Signup and view all the answers

What is the normal volume range of cerebrospinal fluid (CSF) in adults?

90 to 200 mL Signup and view all the answers

Which of the following findings is characteristic in CSF analysis for subarachnoid hemorrhage?

Xanthochromia and elevated red blood cell count Signup and view all the answers

What is a key reason for performing a lumbar puncture in urgent situations?

To check for central nervous system infection or hemorrhage Signup and view all the answers

Which laboratory technique involves the measurement of gases in the blood?

Oxygen and carbon dioxide electrode Signup and view all the answers

What forms of chemistry are measured through different chemical reactions in the lab?

Dyes and reduced forms Signup and view all the answers

Computed tomography is nearly 100% sensitive for diagnosing which condition within the first six hours?

Subarachnoid hemorrhage Signup and view all the answers

Study Notes

Introduction to Clinical Biochemistry & Blood Biochemistry

Clinical biochemistry is the extension of medicine in the laboratory.
It combines medicine and analytical chemistry methods.
It's not just analytical; it's also an interpretative science.
The analytical part measures the level of chemical/biochemical components in body fluids.
The interpretative part diagnoses disease, screens for susceptibility to diseases, and monitors treatment progress.

Diagnosis

A glucose level equal to or less than 100 mg/dL is considered normal.
A fasting glucose test of 126 mg/dL or higher indicates diabetes mellitus.

Screening

PKU screening is a blood test given to newborns 24-72 hours after birth.
Normal blood phenylalanine concentration in newborns is 0.5-1 mg/dL (30-60 μmol/L).
Infants with PKU have phenylalanine values higher than 2 mg/dL (121 μmol/L).

Monitoring

HbA1c measurement monitors dietary control and therapy during diabetes mellitus treatment.
An HbA1c level greater than 9.0% indicates poor diabetes control (normal value less than 5.7%).
Poor diabetes control increases the risk of complications like renal failure, blindness, and neurological damage.

Biological Specimen

The material of clinical biochemistry is a biological sample (specimen/biospecimen).
Clinical biochemistry deals with the measurement of illness-associated chemicals in biological samples (blood, urine, cerebrospinal fluid, etc.).

Chemical Reactions in Clinical Biochemistry

Clinical biochemistry uses chemical/biochemical/immunological reactions to determine the level of various chemical compounds.
Many simple chemical reactions are used to detect and quantify different compounds in specimens.

Best Biological Sample

The ideal biological sample is the tissue where the change occurs.
Tissue use is often impractical due to ethical and logistical reasons; tissue sampling is usually expensive and invasive.

Biological Samples

A biological sample is material analyzed in a clinical biochemistry laboratory.
Biological samples commonly studied include blood, urine, and cerebrospinal fluid (CSF).
Other biological samples include semen/seminal fluid, stool, bronchoalveolar lavage (BAL), breast milk, pleural fluid, pericardial fluid, synovial fluid, cord blood, and meconium.

Advantages of Blood Samples

Blood is the most frequently used biological sample in medicine.
Blood composition changes rapidly in response to tissue alterations.
Obtaining blood samples is minimally invasive.
Blood sample analysis requires relatively simple skills.
Blood sample analysis is generally inexpensive.

Blood

Blood is a tissue mainly located in the circulatory system and circulated by the heart's pumping action.
Blood interacts with almost all tissues in the body.
Intense substance/fluid exchange takes place between blood and tissues.
This exchange determines the composition of the blood.

Components of Blood

Blood contains various components like cells (red and white cells), water, electrolytes, nutrients (glucose, lipids, amino acids, vitamins), proteins (blood proteins, antibodies, enzymes), hormones, and gases (oxygen, carbon dioxide).

Organs Contributing to Blood Composition

The small and large intestines, liver, lungs, and kidneys actively regulate blood composition.

Leakage to the Blood

Tissue molecules leak into the bloodstream due to physiological cell death or tissue damage.
Increased amounts of particular substances (or enzyme activity) in the blood often indicate tissue damage (disease).

ALT and AST Enzymes in Acute Hepatitis

Normal ALT and AST levels are below 40 IU/L.
Viral hepatitis damages liver cells, leading to significantly elevated ALT and AST levels (typically above 400 IU/L).

Alkaline Phosphatase (ALP) Enzyme

ALP is primarily a liver enzyme, but other tissues also produce it.
Blood ALP levels reflect the total ALP activity from all sources in the body.

ALP in Pregnant Women

Normal serum ALP levels in adults are 37-116 U/L.
High ALP activity(2817 U/L) is observed during pregnancy due to placental ALP isoenzyme.
Post-partum ALP levels decline.

Distinguishing Placental ALP

Placental ALP is heat-stable, whereas liver and bone isoenzymes are less stable at high temperatures.
Heat fractionation can help to distinguish the predominant isoenzyme in cases of elevated ALP.

Heat Fractionation

Heat serum samples at 56°C for 15 minutes to observe ALP activity differences compared to unheated samples.

ALP in Children

Total serum ALP activity is used as a biochemical marker for bone formation.
Changes in total serum ALP activity reflect changes in serum Bone-ALP (B-ALP) levels in healthy children.

Reference Ranges (ALP)

Specified reference ranges for ALP activity are provided based on age groups ( <1 month, 1 month - 3 years, 3 - 10 years, 10 - 14 years, 14 - 18 years, >18 years).

Proteins in the Blood

Tissues (especially the liver) produce and secrete proteins into the blood, which play crucial roles.
Decreased levels of certain blood proteins can indicate tissue damage or disease.

Blood Albumin in Hepatic Cirrhosis

Albumin is a crucial blood protein synthesized by the liver.
Liver damage (cirrhosis) reduces albumin synthesis, resulting in decreased blood albumin levels.
Normal albumin levels are 3.5-5.5 g/dL; decreased levels are seen in liver dysfunction.

Blood Composition

Blood consists of plasma (55%), the liquid portion; buffy coat (1%), white blood cells and platelets; red blood cells (44%).

Erythrocyte Count, Hemoglobin Amount, Hct

Erythrocytes (red blood cells) are the most abundant blood cells by volume.
Erythrocyte count, Hct (hematocrit - erythrocyte volume/total volume), and hemoglobin correlate.
These cells primarily consist of hemoglobin.

Blood Counter

Automated instruments used to count blood cells and measure other parameters like hemoglobin and hematocrit.

Blood Parameters and Anemia

Reduced erythrocyte count, hemoglobin amount, and hematocrit indicate anemia. This means the number of red blood cells or hemoglobin levels are lower than normal which inhibits adequate oxygen transport throughout the body.

Increased White Blood Cell Count

High white blood cell count indicates infection.

Reduced Platelet Count

A low platelet count means a delayed blood clotting tendency and increases bleeding risk.

Complete Blood Count (CBC)

A comprehensive blood test measuring various blood components. (A table of potential results and values are available in the document).

Plasma vs. Serum

Plasma is the liquid part of blood containing fibrinogen.
Serum is plasma without fibrinogen. Blood clotting forms fibrin, which is not present in serum.

Whole Blood, Plasma, and Anticoagulants

Whole blood containing anticoagulant is used for blood cell counting and HbA1c measurement.
Plasma is usually used for measurements like fibrinogen and other clotting factors.
Anticoagulants prevent blood clotting.

Serum

Serum is typically used for clinical biochemistry testing because it can be used for a wide range of assays.
A table of various clinical chemistry tests, results, and reference ranges are available for serum (e.g., Urea, Creatinine, Sodium, Potassium, Chloride, Calcium, Phosphate, Uric Acid, Total Bilirubin, Direct Bilirubin, AST, ALT, Total Protein, Albumin, A/G ratio).

Test Panels

Organ-based, metabolism-based, or system-based panels group related lab tests, for example, renal function tests (creatinine, urea, and electrolytes such as calcium, sodium, potassium, and bicarbonate), liver function tests (transaminases, alkaline phosphatase, bilirubin, and albumin), lipid panels (cholesterol, HDL, LDL, and triglycerides), and thyroid panels (TSH, T3, and T4).