(13) Tests and methods for detecting diseases in humans or other animal organisms

See also Plant diseases and defences against pathogens and pests

Observations

Often symptoms of some disease/infection are quite plain to see in us humans and other animals e.g.

we experience a higher than normal temperature due to some fever condition, a headache or a spotty rash.

But, what you see, feel or measure with a thermometer, might not be enough to properly identify the infection causing the disease.

And, particular problems arise if ...

(i) the symptoms are common to several diseases,

(ii) or the symptoms are uncommon.

Therefore it is sometimes necessary to turn to laboratory analysis of some kind e.g. blood tests or tissue cell tests.

 

Laboratory techniques

Samples of body fluids e.g. blood, faeces or tissue from the diseased organism can obtained and visually examined or analysed in various ways e.g.

 

(a) Blood counts

The relative numbers of red blood cells or white blood cells can be important symptoms and help diagnose medical conditions.

A complete blood count is a blood test used to evaluate your overall health and detect a wide range of disorders, including anaemia, infection and leukemia.

If any of the measured concentration of red blood cells, white blood cells (of the immune system) and platelets is abnormal, further investigation would be requires.

 

(b) Urine analysis

Urine analysis can detect urinal infections, kidney or liver disease and diabetes (the latter is indicated by too much glucose in urine - you can actually do a simple dip stick test).

 

(c) Detailed visual microscopic examination of cells

Certain diseases can be detected by examining tissue cells under an optical microscope to look for abnormalities.

Cells of abnormal shape indicate the presence of some disease.

Microorganisms such as bacteria can detected and identified by their appearance.

You can stain the samples on the microscope slide to help show up clearer any specific cell or tissue abnormalities or pathogens - the dye can latch onto and become concentrated on particular structures.

 

(d) Reproducing the pathogen for a more detailed analysis

If the pathogen sample is too small, it can be added to a growth medium to multiply and give a better sample to analyse - either microscopic examination for identification or from DNA analysis (see below).

See Culturing microorganisms like bacteria for more details of the aseptic techniques - to avoid contamination by other microorganisms, therefore avoid identifying the wrong pathogen.

You can also test the pathogen with a selection of antimicrobial compounds to see what kills it - this can help identify the pathogen and what treatment is most likely to be the most effective treatment.

 

(e) Genetic analysis - DNA sequencing

The isolated suspect microorganism sample can be subjected to DNA analysis.

The genetic profile can be matched against a database of pathogen genomes.

Laboratory tests can identify a specific pathogen by adding sections of DNA known to be complementary to the pathogens DNA.

If the added DNA strands bind to the pathogen's DNA, it means that specific pathogen is present, thereby allowing identification.

 

See also Plant diseases and defences against pathogens and pests

---

Key points Source of information is based on textbooks and syllabus-specifications for students taking the AQA GCSE, Edexcel GCSE and OCR GCSE level biology examinations (~US grades 9-10).

Some key ideas and examples about testing for diseases

Detecting Diseases in Humans and Animals

1. Why Detect Diseases?

• Early detection allows for faster treatment, better outcomes, and prevention of spread.

• Helps distinguish between infectious and non-infectious diseases.

• Supports public health monitoring and epidemic control.

---

2. Methods of Disease Detection

A. Recognising Symptoms

• First step in diagnosis.

• Symptoms like fever, rash, fatigue, or swelling may indicate infection or other conditions.

• Some diseases have specific symptoms (e.g. chickenpox rash), while others are non-specific (e.g. fatigue).

B. Medical History and Physical Examination

• Doctors ask about:

  • Lifestyle, travel history, family history, and previous illnesses.

• Physical checks include:

  • Temperature, heart rate, blood pressure, and visible signs (e.g. swelling, rashes).

C. Laboratory Tests

These are more accurate and confirm a diagnosis:

• Blood Tests:

  • Detect infections, hormone levels, organ function, and immune responses.

  • Can identify antibodies or antigens linked to specific diseases.

• Urine and Stool Tests:

  • Detect infections, kidney/liver problems, or parasites.

• Swabs and Cultures:

  • Swabs from throat, nose, or wounds are cultured to grow and identify bacteria or fungi.

• Microscopy:

  • Cells or pathogens are viewed under a microscope (e.g. malaria parasites in blood).

• PCR (Polymerase Chain Reaction):

  • Detects genetic material of viruses or bacteria (e.g. COVID-19, HIV).

  • Very sensitive and specific.

• Monoclonal Antibody Tests:

  • Used in pregnancy tests, COVID-19 lateral flow tests, and cancer detection.

  • Bind to specific antigens to confirm presence of a disease.

D. Imaging Techniques

• X-rays: Detect broken bones, lung infections (e.g. pneumonia).

• Ultrasound: Used for soft tissues and pregnancy.

• MRI and CT Scans: Provide detailed images of internal organs and detect tumours or internal damage.

E. Biopsies

• A small tissue sample is taken and examined under a microscope.

• Used to diagnose cancer, inflammatory diseases, or infections.

---

3. Importance in Understanding Human Biology

• Reinforces how the immune system responds to disease.

• Shows how technology and biology work together in modern medicine.

• Highlights the importance of early detection in preventing complications.

• Encourages awareness of non-communicable diseases (e.g. cancer, diabetes) and communicable diseases (e.g. TB, flu).

• Supports understanding of epidemiology and public health.

---

Exam Tips

• Be able to name and describe at least 3 diagnostic methods.

• Understand how monoclonal antibodies are used in testing.

• Explain the advantages of early diagnosis.

• Link detection methods to specific diseases (e.g. PCR for viruses, X-rays for pneumonia).

---

Some examples in more detail - if you are interested

Real-Life Examples of Disease Detection Methods

1. PCR Testing – COVID-19

• During the pandemic, PCR (Polymerase Chain Reaction) tests were widely used to detect the genetic material of the SARS-CoV-2 virus.

• These tests became the gold standard for diagnosing COVID-19 due to their high sensitivity and accuracy.

2. Lateral Flow Tests – Pregnancy and COVID-19

• Pregnancy tests use monoclonal antibodies to detect the hormone hCG in urine.

• Similarly, COVID-19 rapid antigen tests (lateral flow tests) detect viral proteins using monoclonal antibodies — giving results in minutes.

3. Blood Tests – Diabetes and HIV

• People with diabetes regularly use blood glucose tests to monitor sugar levels.

• HIV diagnosis often begins with a blood test that detects antibodies or antigens related to the virus.

4. Imaging – Cancer and Pneumonia

• X-rays are used to detect lung infections like pneumonia or tuberculosis.

• MRI and CT scans help identify tumours, internal bleeding, or organ damage — crucial in cancer diagnosis and treatment planning.

5. Biopsies – Cancer Diagnosis

• A biopsy involves removing a small tissue sample for microscopic examination.

• It’s commonly used to confirm skin cancer, breast cancer, or bowel cancer.

6. Genetic Testing – Inherited Disorders

• Newborn screening often includes genetic tests for conditions like cystic fibrosis or sickle cell anaemia.

• Adults may undergo genetic testing to assess risk for diseases like BRCA-related breast cancer.

7. AI-Assisted Detection – Eye Disease and Cancer

• AI is now used to detect diabetic retinopathy from retinal scans and early-stage lung cancer from CT images — sometimes spotting signs that doctors might miss.

---

Learning objectives for this section on detecting and testing for pathogens

Know some test methods for detecting diseases to help in diagnosis of human conditions e.g. blood counts, urine analysis, microscopic examination of cells and DNA sequencing of samples of the pathogen.

---

WHAT NEXT?

TOP OF PAGE

INDEX of biology notes on the body's defence mechanisms against infections from pathogens

INDEX of all my BIOLOGY NOTES

BIG website, try using the [SEARCH BOX], maybe quicker than the many indexes!

Basic Science Quizzes for UK KS3 science students aged ~12-14, ~US grades 6-8

Biology * Chemistry * Physics for UK GCSE level students aged ~14-16, ~US grades 9-10

Advanced Level Chemistry for pre-university age ~16-18 ~US grades 11-12, K12 Honors

Find your GCSE/IGCSE science course for more help links to all science revision notes

email doc brown - comments - query?

---

Explaining importance of tests for detecting & diagnosing diseases in GCSE level biology, What you need to know about tests for detecting & diagnosing diseases for GCSE level biology, Explaining use of tests for detecting & diagnosing diseases knowledge in GCSE level biology, Examples of tests for detecting & diagnosing diseases explained when studying GCSE level biology, What is the significance of tests for detecting & diagnosing diseases in GCSE level biology, describing explaining theory of tests for detecting & diagnosing diseases when studying GCSE level biology, exam revision notes for tests for detecting & diagnosing diseases, online help for understanding tests for detecting & diagnosing diseases in GCSE biology, what do I need to learn about tests for detecting & diagnosing diseases? what do I need to know about tests for detecting & diagnosing diseases for GCSE biology exams, how to prepare for questions on tests for detecting & diagnosing diseases in GCSE biology examination? tests for detecting & diagnosing diseases for syllabus-specifications for students taking the IGCSE/GCSE level biology examinations, summary revision notes key points on tests for detecting & diagnosing diseases for students studying AQA igcse/gcse biology notes on tests for detecting & diagnosing diseases, Edexcel gcse biology notes on tests for detecting & diagnosing diseases,  OCR 21st century GCSE biology notes on tests for detecting & diagnosing diseases, OCR gateway GCSE biology notes on tests for detecting & diagnosing diseases, WJEC gcse biology notes on tests for detecting & diagnosing diseases, CCEA gcse biology notes on tests for detecting & diagnosing diseases, CIE Cambridge igcse biology, notes on tests for detecting & diagnosing diseases useful for US grade 9-10 biology student courses, Explaining importance of techniques for diagnosing diseases in GCSE level biology, What you need to know about techniques for diagnosing diseases for GCSE level biology, Explaining use of techniques for diagnosing diseases knowledge in GCSE level biology, Examples of techniques for diagnosing diseases explained when studying GCSE level biology, What is the significance of techniques for diagnosing diseases in GCSE level biology, describing explaining theory of techniques for diagnosing diseases when studying GCSE level biology, exam revision notes for techniques for diagnosing diseases, online help for understanding techniques for diagnosing diseases in GCSE biology, what do I need to learn about techniques for diagnosing diseases? what do I need to know about techniques for diagnosing diseases for GCSE biology exams, how to prepare for questions on techniques for diagnosing diseases in GCSE biology examination?

---