Background reading by Professor Omar Hasan Kasule MB ChB(MUK), MPH
(Harvard), DrPH (Harvard)
1.0 DIAGNOSIS
1.1 Definition
The term diagnosis is derived from the Greek
word ‘gnosis’ which means knowledge. It basically refers to determining if a
disease or disorder exists and to define its nature. It involves analysis of
data on symptoms, signs, and specific investigations. Background knowledge of
disease epidemiology and disease risk factors in an area at a given point in
time helps in arriving at a correct diagnosis.
1.2 Probability in diagnosis
It may not be possible to reach conclusion
about one diagnosis and one may have to identify several diagnoses and arrange
them in order of likelihood. Therapeutic interventions are undertaken on the
basis of a leading diagnosis and alternate diagnoses. The legal basis for
intervention in such cases is ghalabat al dhann or predominant
conjecture. Further manifestations of the disease process or response to
therapy may finally allow definitive determination of the diagnosis. There are
situations in which the final diagnosis cannot be determined until after death
when post-mortem examination reveals the true cause of death.
1.3 Basis of diagnosis
Historically diagnosis relied more on symptoms.
With development of systematic methods of clinical examination more reliance
was placed on signs. However major breakthroughs in diagnosis were achieved
when medical technology provided a wide array of accurate and reliable
laboratory and radiological investigations. Instruments were also developed to
be able to make more accurate observation of signs both inside and outside the
body. Further refinements in diagnosis are going to be based on technological
developments but will never supplant the role of careful history taking for
symptoms and clinical examination for signs.
1.4 Use of computers
Computers are being used increasingly in the
diagnostic process to process and summarize massive volume of quantitative data
and compute probabilities of various diagnostic possibilities. The human mind
is still needed to make the final diagnosis because the computer in the end is
a machine and does not fully encompass all the creative and innovative thinking
skills found in a human physician. Physicians acquire diagnostic competence
through long periods of practical clinical training because in the end medicine
is an art. Computers and other machines cannot have this clinical competence.
1.5 Hypotheses
Making a diagnosis requires summarizing and
analyzing information collected from history, physical examination, and various
investigations. The clinician initially develops a series of possible
alternative diagnoses called the differential diagnosis. With use of further
information from investigations or sometimes response to therapy, the
diagnostic possibilities are narrowed down even further. Sometimes a diagnosis
is arrived at by elimination. Computers using algorithms developed by
experienced clinicians can be used to aid the diagnostic process.
2.0 CLINICAL HISTORY
2.1 Consent and confidentiality
Patients have to consent before their medical
history can be taken otherwise the physician will be trespassing on privacy and
may be accused of spying, tajassus. The permission to take history is
needed even if a proxy such as a spouse or a parent volunteers the history. The
same applies to information collected from previous records. Any information
obtained from or about a patient is confidential and its unauthorized
disclosure is a breach of confidentiality.
2.2 Nasiihat and Da’awat
The purpose of history taking is to discover
the social or personal antecedents of disease as well as the natural history of
the disease. This involves considerable probing into personal life and privacy.
It provides a golden opportunity for both physician and patient to face
diseases of the heart, amraadh al qalb, that affect physical health. The
diseases of the heart may be transgression, dhulm; neglect, ghaflat;
loss of self-control and following passions (sex, drug, and alcohol-addiction).
There is an opportunity for the physician to exercise the function of da’wah
and for the patient to make repentance, taubat.
2.3 Legal issues
History taking is also an opportunity for
discovery of legal complications such as foster relations that prohibit
marriage, defective marriages concluded during ‘iddat. In complicated
medical conditions, history taking may be an opportunity for discussing costs
of medical care with the patient. The physician taking history may face a major
ethical dilemma when in the course of taking history, the patient volunteers
information about a criminal action that should be prosecuted. If the physician
keeps the information to himself, he is not fulfilling the duty required of him
as a citizen to report crime to the authorities.
2.4 Communication skills
Successful history taking requires good
communication skills and careful observation of non-verbal clues. Accurate
history depends on the honesty and memory of the patient. Patients may not want
to reveal some information that they consider embarrassing or that they
mistakenly consider irrelevant to the presenting disease condition. Patients
may forget some information or confuse it. The interviewer must be tactful and
sensitive in probing for relevant information and may have to adopt various
strategies to help the patient’s memory. Questions may be open-ended or closed.
Sometimes the interviewer may just have to keep quiet and listen actively as
the patient talks to be able to pick up useful clues. Interrupting patients is
a frequent problem of interviewers who pressed for time would like to keep the
interview as short as possible. Patients with underlying emotional problems may
only verbalize physical symptoms and it requires tact and establishment of rapport
to get them to talk about their inner worries and feelings.
2.5 Elements of a medical history
A complete medical history consists of an
account of the present illness and its evolution since first noticed, relevant
past medical history, family history, social history, psychological history,
and history of occupational and environmental exposures.
Account of the presenting illness covers recent
changes in health status, associated triggering factors, and all changes that
have occurred from the start until presentation to the physician. The account
is not completed on the first interview. In the course of clinical examination
or treatment signs may be identified that suggest eliciting more information
about the causes and course of the presenting illness.
Past medical history covers health status and
disease experiences as back as can be remembered. It includes medical,
surgical, and psychiatric conditions. Both severe illnesses requiring
hospitalization and less severe ones treated symptomatically or not treated at
all need to be recorded if they have relevance to the presenting illness. The
interviewer must have an extensive knowledge of disease epidemiology and
disease pathophysiology to known what relevant questions to ask.
Family history elicits information about
diseases in immediate family members because the presenting illness may have a
familial hereditary basis or an environmental basis in the domicile of the
patient.
Social history elicits information about social
factors that are relevant to disease such as marital status, education,
lifestyle (eg alcohol, drugs, smoking), and beliefs.
Occupational and environmental exposures should
be documented for a long time before the presenting illness because for chronic
diseases the causative agent may act years before the presenting illness.
History taking is completed by a thorough
review of the organ systems. The patient is asked specific questions about
symptoms in each system that may have relevance to the presenting complaint.
3.0 CLINICAL STATE EXAMINATION
3.1 Consent and confidentiality
The issues of consent and confidentiality
discussed above for history taking are also relevant to clinical or mental
examinations. A patient can only be examined against his or her consent only if
there is a necessity, dharuurat. The necessity may relate to the life of
the patient or may be in public interest such as examining a suspected criminal
for evidence about the crime. Mental patients can are not legally competent to
give consent; the necessary consent could be obtained from a guardian, wali.
Examination by a caregiver of the opposite gender requires special
consideration. It is always preferable that physicians of the same gender carry
out the examination. A physician of the opposite gender can be used only if a
situation of necessity arises. A chaperone must be present. Examination limited
to what is necessary. Al nadhar ila al awrat bi qadar al dharuurat.
The physician should allay the anxiety of
patients being examined.
3.2 Contents of physical examination
Clinical examination traditionally consisted of
inspection, palpation, percussion, and auscultation. These processes have now
become more sophisticated because of availability of various diagnostic
instruments developed by modern medical technology.
Inspection is visual observation before
touching a patient. The following are the main points of observation: general
appearance, nutritional status, symmetry, posture, wounds and signs of external
injury, mood and behavior. Many useful clues can be obtained from looking at
various parts of the body. Hair loss may indicate infection, hormonal
disturbances, or anti-cancer chemotherapy. Clubbed nails indicate chronic
cardiovascular or respiratory disease. Pitted nails indicate psoriasis. The
skin may have benign moles or malignant cancers.
Palpation is using the physician’s hand and
sense of touch to elicit signs from structures on the surface of the body or
organs inside the body. Light palpation can detect tenderness, muscle spasm,
rigidity and hardness. Deep palpation can define the size, shape, and
consistency of internal structures. Vibratory sensations can also be detected
on palpation.
Percussion involves tapping on the surface and
listening to the sound produced. Internal structures filled with air, water, or
solidified tissue have different resonances that a trained examiner can
identify and characterize.
Auscultation is listening to sounds from the
heart, blood vessels, lungs, and intestines. Normal sounds made by closure of
the various heart valves can be heard and can be distinguished. Murmurs
indicate abnormal blood flow in the heart. Bruits are produced when blood flows
through an occluded blood vessel. In a healthy lung air flows smoothly
producing normal breath sounds. Wheezes are produced in cases of obstruction.
Crackles (also called rales) are produced when there is excessive fluid in the
lungs. Inflammation of the pleura produces creaking sounds. No sounds are heard
when the bowel is paralyzed and there are no bowel movements. In intestinal
obstruction high pitch sounds are heard. In intestinal hyperactivity the sounds
are greatly enhanced.
In an emergency, the sequence of history-taking
and physical examination described above cannot be followed. Priority is given
to examining the respiratory, circulatory, and nervous systems because they are
essential for life. The respiratory system is examined to assure that there is
adequate oxygenation. The circulatory system is examined to ensure that there
is an adequate cardiac output. The nervous system is examined by observing
response to external stimulation. The size and reaction of pupils to light
indicate the state of consciousness.
3.3 Pediatric examinations
Pediatric examinations involve additional
observations. The Agar score is assessed at birth and indicates overall
prognosis. Growth is assessed as height and weight being compared to standard
charts. At birth the average length is 50 cm. It increases by 50% at 12 months
and doubles at 4 years. From year 2 until the adolescent growth spurt height
increases by 5 cm every year. Birthweight doubles at 4-5 months and triples at
12 months. It increases by 2.3 kg every year from year 2 to the adolescent
growth spurt. The Denver Developmental Screening Test assesses psycho-social
development that includes language and social skills. Children are also
examined for vision, hearing, and dental development.
3.4 Geriatric examination
Geriatric examinations call for special skills.
With age there are changes in body structure and function. Cardiac changes
include reduced cardiac output and decreased blood flow to the organs.
Respiratory changes are decrease of alveoli and weakening of respiratory
muscles. Gastro-intestinal changes include: decreased gastric acid secretion,
decreased intestinal motility with frequent complaints of constipation, slower
drug metabolism, and loss of teeth resulting in impaired mastication and
chewing of food. Excretion is decreased with lower urinary output associated
with a decreased number of nephrons. Musculoskeletal changes are decreases
muscle mass, and osteoporosis. Endocrine changes are decreased thyroid and
adrenal function, decrease insulin production, and increased insulin
resistance. Neurological changes are slower nerve conduction, loss of brain
mass, decrease cerebral blood flow, depression, decreased sleep, and dementia.
Sensory changes are: decreased visual acuity, decreased smell and taste
sensation. The elderly become shorter because of narrowing of intervertebral
discs.
3.5 Mental state examination
Psychiatric examination assesses stress,
anxiety disorders, mood disorders, and psychotic disorders. Anxiety disorders
include panic disorder, generalized disorder, post-traumatic stress disorder,
phobic disorder, and obsessive-compulsive disorder. Mood disorders are major
depression, dysthymia (minor depression), bipolar disorder, and cyclothymia
(chronic minor form of the bipolar disorder).
Psychological tests are used in psychiatric
diagnosis. The Minnesota Multiphasic Personality Inventory (MMPI) is a
questionnaire used to assess personality characteristics. The Mini-Mental State
Examination assesses cognitive function. The Rorschach test assesses
personality functioning and emotional aberrations. The Thematic
Appreciation Test (TAT) assesses anxiety, personal conflict, and interpersonal
relations. Depression is assessed using the Beck Depression Inventory and the
Zung Self-Rating Depression Scale.
4.0 LABORATORY INVESTIGATIONS
4.1 Purpose
The purposes of laboratory investigation are to
provide base-line information, establish a diagnosis, exclude alternative
diagnoses, evaluate severity, plan treatment, and predict prognosis. Results of
laboratory tests are used in the process of decision making at all stages of
clinical management. Usually treatment is based a provisional diagnosis. The
final or discharge diagnosis is confirmed towards the end of the disease
episode. The test must be sensitive and specific. Due to availability of
automatic processing of biological samples physicians no longer ask for
specific tests but ask for a battery of tests. This risks producing false
positive results on the basis of chance alone. The range of normal results
varies with the test technique and with age or race. The results of laboratory
investigations have the same requirements for confidentiality as history and
clinical examination.
4.2 Types of investigations
Hematological investigations are carried out for anemia,
hemoglobinopathies, bleeding disorders, blood grouping, and blood
compatibility. A complete blood count (CBC) consists of number of red blood
cells, number of white blood cells with a differential count, hemoglobin
concentration, hematocrit, red cell volume (MCV), and platelet count.
Coagulability is assessed by the prothrombin test, the partial thromboplastin
time, plasma fibrinogen, and blood clotting factors. The erythrocyte
sedimentation rate (ESR) is a non-specific indicator of inflammation. The
Coombs or antiglobulin test (AGT) tests red blood cell compatibility for
purposes of transfusion.
Histopathological diagnosis describes the pathological process
and indications of possible initial insults.
Microbiological investigations are bacteriological,
virological, and parasitological.
Biochemical investigations include renal function tests,
liver function tests, fluids, electrolytes, and acid-base balance. Fasting
blood glucose level and the glucose tolerance test are used to diagnose
diabetes mellitus. Gastrointestinal absorption is assessed by measuring urinary
excretion of ingested radioactive substances or urinary excretion of D-xylose,
a substance that is not metabolized by the body. Intestinal absorption can also
be assessed by the amount of fat in stool collected over 3 days following a
fat-rich diet. Levels of various toxins are measured in serum or other body
fluids using specialized biochemical tests.
Immunological tests assess presence and concentration of
antibodies.
Genetic/chromosomal analysis is used increasingly in disease diagnosis.
Careful family history taking and physical examination are used to construct a
family pedigree for a specific disease. Among specific genetically-related
tests are: chromosome karyotyping, enzyme assays, hormonal assays, aminoacid
assays, blood grouping and typing, immunoglobulin assays, and hemoglobin
electrophoresis. Prenatal tests for congenital genetic disease is controversial
because it encourages abortion. Genetic tests pose a special problem because
genetic findings in a patient give information about genetic make-ups of
parents and siblings. Thus disclosure of the patient’s genetic findings may
require in addition the consent of the relatives concerned.
Biological markers are used in diagnosis and follow up of disease
treatment the commonest being: HCG for trophoblastic tumors &
hepatocellular carcinoma; AFP, HCG, HBD, PLAP for germ cell tumors; CEA for GIT
tumors, CA125 for ovarian cancer; PSA for prostate cancer; CA and S-3 for
breast cancer; and SCC for skin cancer. analysis is used increasingly in
disease diagnosis.
Urine examination includes assessment for color,
turbidity, cells, urinary casts, specific gravity, bilirubin, urobilinogen,
hemoglobin, glucose, ketone bodies, pH, protein, and bacteria.
Fecal examination consists of fecal occult blood
testing (FOBT), culture for microorganisms, and examination for parasites.
Cerebrospinal fluid is examined for white blood cells, culture for
microorganisms, glucose, protein, and fluid pressure. Gastric juice is examined
for blood and is cultured for microorganisms.
Semen is examined for number, motility, and
normality.
5.0 RADIOLOGICAL/IMAGING INVESTIGATIONS
5.1 Non-invasive investigations
Radiological investigations reveal a lot of
information with minimal invasion. The commonest radiological examination is
the plain X-ray film. It may be enhanced by used of barium or air to show
inside structures better. Computed tomography (CT scan) produces a
cross-section of the body at various levels. Ultrasonography uses sound
waves to define internal structures. It is quick and cheap but is not as
accurate as CT scan or MRI. Magnetic resonance imaging (MRI) uses magnetic
fields and radiowaves to produce images of internal structures. It is more
accurate than CT scan but is more expensive and more cumbersome to use. CT can
and MRI produce 2-dimensional images but newer techniques are able to produce
3-dimensional images. Mammography is used to screen for breast cancer. The
results of radiological investigations are confidential. Images that show the
shape of the body parts can be considered showing awrat and should not be seen
except by authorized people only and for specific purposes. Digital subtraction
angiography and positron emission tomography are also used.
5.2 Invasive
investigations
Invasive investigations carry a higher risk to
the patient; their benefits should be carefully weighed against the benefits.
The commonest investigations are: endoscopy (nasophayngolaryngoscopy,
colonoscopy, sigmoidoscopy, esophagogastroduodenoscopy,
cholangiopancreatoscopy, colposcopy, and peritoneal laparascopy), cardiac
catheterization and angiography, biopsy (incision, excision, needle,
aspiration, and abrasion as in the Pap smear test), autopsy, and diagnostic /
exploratory laparatomy. These investigations should be carried out only if
there is a clear necessity, dharuurat.
6.0 INSTRUMENTAL INVESTIGATIONS
The electrocardiogram (ECG) assesses cardiac
electrical conduction. The electroencephalogram (EEG) measures electrical
activity in the brain. The echocardiogram uses sound waves to assess structure
and movement of the heart and is more useful in children. Myocardial perfusion
imaging uses radioactive thallium injected intravenously to study heart
pathology detected by disturbance in radioactive uptake. Electromyography
assesses electrical conductivity in muscles.
