9. Clinical Laboratory Tests: A Complete Guide for Pharmacy Students

CLINICAL LABORATORY TESTS

Welcome, future pharmacists and healthcare professionals!

As a pharmacy educator with years of experience teaching hospital and clinical pharmacy, I have always emphasized that clinical laboratory tests are essential tools for diagnosing, monitoring, and managing diseases. These tests involve collecting a sample of blood, tissue, or other biological matter from the patient by a skilled medical professional. The sample is then sent to the clinical laboratory where it is examined by specially trained medical professionals using suitable equipment. Understanding these tests is crucial for pharmacists to interpret lab reports and make informed clinical decisions.

In this comprehensive guide, I will take you through the various clinical laboratory tests used in the evaluation of disease states. We will explore haematological tests, liver function tests, renal function tests, thyroid function tests, cardiac tests, and pulmonary function tests. By the end of this article, you will have a thorough understanding of the significance and interpretation of test results. Let us begin.

INTRODUCTION TO CLINICAL LABORATORY TESTS

Clinical laboratory tests are diagnostic procedures that involve the collection and analysis of biological samples such as blood, urine, or tissue. These tests are performed to detect, diagnose, and monitor diseases, as well as to evaluate the effectiveness of treatment. The results of these tests provide valuable information about the patient’s health status and guide clinical decision-making.

The various clinical laboratory tests discussed in this chapter include haematological tests, liver function tests, renal function tests, thyroid function tests, tests associated with cardiac disorders, and pulmonary function tests. Each of these tests has specific normal ranges, and deviations from these ranges can indicate various disease states.

HAEMATOLOGICAL TESTS

Haematological tests are among the most commonly ordered laboratory tests. They evaluate the cellular components of blood and provide information about various blood disorders and systemic diseases.

Hemoglobin (Hb) Value

Haemoglobin is the red-coloured pigment of blood. It consists of globin (96%) and haem (the iron-containing pigment, 4%). Its concentration is expressed in gram percentage.

Normal Range:

• Male: 14 to 18 g/dL
• Female: 12 to 16 g/dL
• Infant: 9.5 to 13 g/dL

Significance: Values of haemoglobin below the normal range indicate conditions of anaemia and leukaemia, while values above the normal range indicate polycythaemia. Haemoglobin levels are essential for assessing the oxygen-carrying capacity of blood.

Red Blood Cell (RBC) Count

RBCs are abundantly present in the blood and are red-coloured due to the presence of haemoglobin. RBCs are formed in the bone marrow.

Normal Range:

• Male: 4.5–5.5 million/mm³
• Female: 3.5–5.5 million/mm³
• Children: 4.0–5.5 million/mm³

Significance: RBC count above the normal range indicates heart ailment, polycythaemia, cholera, diarrhoea, polyuria, and severe burns. RBC count below the normal range indicates anaemia and leukaemia.

Hematocrit (HCT)

Hematocrit estimates the percentage by volume of RBCs in a whole blood sample. For example, 40% Hct indicates that a 100 mL blood sample has 40 mL of blood cells.

Normal Range:

• Male: 40–50%
• Female: 37–47%
• Infant: 32–42%

Significance: Two small and same quantities of blood samples are compared. One sample is centrifuged and compared to the first sample to obtain a percentage value. If the Hct value is abnormal, the RBC count may also be abnormal. If the RBC count is normal, the average size of RBC will possibly be too small. Shock, dehydration, haemorrhage, or excessive IV fluid administration can decrease the value of Hct.

Reticulocyte Count

This test is used to evaluate the definite numbers of reticulocytes (immature RBCs) in blood.

Normal Range: Approximately 1% of normal RBC counts (50,000); results vary between 0.5–1.5%.

Significance: The reticulocyte count indicates the production of RBCs by bone marrow. An elevation from the normal indicates that the body is reacting to pathologies like haemorrhage, anaemia, haemolysis, or other disease processes. Lowered reticulocyte count indicates anaemia or any associated disorder.

Sickle Cell or HbS Test

It is used to identify sickle cells, which are badly distorted, rigid erythrocytes that can slow down blood flow.

Normal Range:

• 6 months to 15 years: 7–140 ng/mL
• 2 to 5 months: 50–200 ng/mL
• 1 month old: 200–600 ng/mL
• Neonates: 25–200 ng/mL

Iron and Total Iron-Binding Capacity (TIBC)

To measure the quantity of iron bound to transferrin in blood plasma, an iron assay is done. TIBC determines the quantity of iron that appears in plasma if total transferrin were saturated with iron.

Normal Range:

• Serum Iron: Male 50–150 μg/dL, Female 35–145 μg/dL
• TIBC: Male and female 250–400 μg/dL
• Saturation: Male and female 14–50%

Significance: Elevated TIBC level indicates low body iron, late pregnancy, and iron deficiency anaemia. Lower-than-normal TIBC level indicates haemolytic anaemia.

White Blood Cell (WBC) Count

Normal Range: 6000–10,000/mm³

Significance: Elevated WBC count (leukocytosis) indicates bacterial infection, inflammation, or leukaemia. Decreased WBC count (leukopenia) indicates viral infections, bone marrow depression, or autoimmune disorders.

Differential Leukocyte Count (DLC)

Cell Type	Normal %	Significance
Neutrophils	60–70%	Increased in bacterial infections
Eosinophils	1–4%	Increased in allergies, parasitic infections
Lymphocytes	20–30%	Increased in viral infections

Erythrocyte Sedimentation Rate (ESR)

Normal Range: Male ≤15 mm/hr, Female ≤20 mm/hr

Significance: Elevated ESR indicates inflammation, infection, autoimmune disorders, or malignancy.

Platelet Count

Normal Range: 150–400 × 10⁹/L

Significance: Decreased platelet count (thrombocytopenia) indicates bleeding disorders, dengue, or bone marrow depression. Increased platelet count (thrombocytosis) indicates inflammation or myeloproliferative disorders.

LIVER FUNCTION TESTS (LFT)

Liver function tests assess the health of the liver and detect liver diseases.

Serum Bilirubin

Normal Range: 0.3–1.3 mg/dL

Significance: Elevated bilirubin indicates jaundice, liver disease, or bile duct obstruction.

Serum Proteins

Normal Range: 6–8 g/dL

Significance: Decreased protein indicates liver disease, malnutrition, or kidney disease.

Alkaline Phosphatase (ALP)

Normal Range: 29–92 IU/L

Significance: Elevated ALP indicates liver disease, bile duct obstruction, or bone disorders.

SGOT/SGPT (AST/ALT)

Significance: Elevated SGOT/SGPT indicates liver cell damage, hepatitis, or drug-induced liver injury.

Lipid Profile

Normal Range: Total cholesterol less than 200 mg/dL

Significance: Elevated cholesterol indicates risk of cardiovascular disease and atherosclerosis.

RENAL FUNCTION TESTS (RFT)

Renal function tests evaluate kidney function and detect kidney diseases.

Urine Analysis

Physical and chemical examination of urine to detect abnormalities such as protein, glucose, blood, and pus cells.

Blood Urea Nitrogen (BUN)

Normal Range: 10–12 mg/dL

Significance: Elevated BUN indicates kidney dysfunction, dehydration, or high protein intake.

Serum Creatinine

Normal Range: 1–2 mg/dL

Significance: Elevated creatinine indicates kidney dysfunction and impaired filtration.

Creatinine Clearance

Normal Range: 90–139 mL/min

Significance: Decreased creatinine clearance indicates reduced glomerular filtration rate and kidney impairment.

THYROID FUNCTION TESTS

Thyroid function tests assess the function of the thyroid gland.

Thyroid Stimulating Hormone (TSH)

Normal Range: 0.4–4.0 mU/L

Significance: Elevated TSH indicates hypothyroidism; decreased TSH indicates hyperthyroidism.

T3 (Triiodothyronine)

Normal Range: 100–200 ng/dL

Significance: Elevated T3 indicates hyperthyroidism; decreased T3 indicates hypothyroidism.

T4 (Thyroxine)

Normal Range: 5–11 µg/dL

Significance: Elevated T4 indicates hyperthyroidism; decreased T4 indicates hypothyroidism.

CARDIAC TESTS

Cardiac tests evaluate heart function and detect cardiac disorders.

Pulse Rate

Normal Range: 70–80 beats/min

Significance: Abnormal pulse rate indicates cardiac arrhythmias or other heart conditions.

Creatine Phosphokinase (CPK)

Normal Range: 10–120 mcg/L

Significance: Elevated CPK indicates myocardial infarction, muscle damage, or heart attack.

Troponin

Significance: Elevated troponin indicates myocardial infarction (heart attack). It is a highly specific marker for cardiac injury.

PULMONARY FUNCTION TESTS

Pulmonary function tests evaluate lung function and detect respiratory disorders.

Spirometry

Measures the volume and flow of air during breathing.

Lung Capacity

Measures the total volume of air the lungs can hold.

Vital Capacity

Measures the maximum amount of air that can be exhaled after a maximum inhalation.

FEV and FVC

FEV (Forced Expiratory Volume) and FVC (Forced Vital Capacity) are used to diagnose obstructive and restrictive lung diseases such as asthma and COPD.

FLUID AND ELECTROLYTE BALANCE

Fluid and electrolyte balance is essential for maintaining normal body functions.

• Total body water: 60% of body weight
• Intracellular fluid: 40%
• Extracellular fluid: 20%

Electrolytes: Maintain fluid balance and support nerve and muscle function. Common electrolytes include sodium, potassium, calcium, and chloride.

Disorders of Fluid and Electrolyte Balance

• Dehydration: Dry skin, low BP → treated with ORS and IV fluids
• Fluid Volume Excess: Edema, weight gain → treated with diuretics
• Water Intoxication: Confusion, seizures → fluid restriction

A TEACHER’S PRACTICAL INSIGHTS

Over my years of teaching, I have developed a few key insights about clinical laboratory tests that I always share with my students:

• Understand normal ranges: Knowing the normal ranges for each test is essential for interpreting results and identifying abnormalities.
• Consider the clinical context: Lab results must be interpreted in the context of the patient’s clinical presentation, medical history, and medications.
• Monitor trends: A single abnormal result may not be significant, but a trend over time can provide valuable diagnostic information.
• Stay updated: Laboratory reference ranges can vary between laboratories. Always refer to the specific reference ranges provided by the testing laboratory.

FREQUENTLY ASKED QUESTIONS (FAQs)

1. What are clinical laboratory tests?

Clinical laboratory tests are diagnostic procedures that involve collecting and analyzing biological samples to detect, diagnose, and monitor diseases.

2. What is the normal range for hemoglobin?

Normal hemoglobin levels are 14–18 g/dL for males and 12–16 g/dL for females.

3. What does elevated WBC count indicate?

Elevated WBC count (leukocytosis) indicates bacterial infection, inflammation, or leukaemia.

4. What does elevated bilirubin indicate?

Elevated bilirubin indicates jaundice, liver disease, or bile duct obstruction.

5. What does elevated creatinine indicate?

Elevated creatinine indicates kidney dysfunction and impaired filtration.

6. What is the significance of troponin?

Elevated troponin indicates myocardial infarction (heart attack) and is a highly specific marker for cardiac injury.

7. Why is fluid and electrolyte balance important?

Fluid and electrolyte balance is essential for maintaining normal nerve function, muscle contraction, and overall body homeostasis.

SUMMARY

Clinical laboratory tests are essential tools for diagnosing, monitoring, and managing diseases. Key tests include haematological tests (hemoglobin, RBC count, WBC count, platelets), liver function tests (bilirubin, SGOT/SGPT, ALP), renal function tests (creatinine, BUN, creatinine clearance), thyroid function tests (TSH, T3, T4), cardiac tests (CPK, troponin), and pulmonary function tests (spirometry, FEV, FVC).

Understanding the normal ranges and clinical significance of these tests is crucial for healthcare professionals to make informed clinical decisions and provide optimal patient care.

As I always tell my students: “Clinical laboratory tests are the window to the body’s health. Learn to interpret them, and you will understand the language of disease.”

REFERENCES & FURTHER READING

• Government of India. (1948). The Pharmacy Act, 1948. Ministry of Health and Family Welfare.
• World Health Organization (WHO). (2023). Clinical Laboratory Guidelines. Retrieved from WHO Official Website.
• International Pharmaceutical Federation (FIP). (2023). Clinical Pharmacy Practice Guidelines. Retrieved from FIP Official Website.
• American Society of Health-System Pharmacists (ASHP). (2023). Clinical Laboratory Test Interpretation Resources. Retrieved from ASHP Official Website.
• National Institutes of Health (NIH). (2023). Laboratory Test Reference Ranges. Retrieved from NIH Official Website.

Disclaimer: This article is for educational purposes only and does not constitute medical or legal advice. Always consult qualified healthcare professionals and regulatory authorities for professional and legal matters.