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