LMP299Y1 Lecture Notes - Lecture 1: Transfusion Medicine, Differential Diagnosis, Blood Transfusion

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Published on 19 Jan 2015
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LMP301 Lecture 1
Introduction to the Biochemistry of Human Disease
-societal role of laboratory medicine
-disease states and classifications
-reason that laboratory tests are ordered
-testing process and variables which affect lab tests and results
How to Determine Sick vs. Healthy
-initial assessment
family history
recent events
complaints
physical signs and symptopms
diagnostic testing (lab and imaging)
-this assessment can determine a working diagnosis that can then be narrowed down
-most initial assessment does not include diagnostic testing – this is usually after a working diagnosis has
been determines (to obtain a differential diagnosis)
-differential diagnosis – narrowing of possibilities down to a single one (which is then usually treated)
What is Disease?
-multiple definitions
characteristic train of symptoms
pattern of response to a living organism to some form of injury
injury – starvation, poisoning, infection, stress, depression, trauma, etc.
Definitive Diagnosis
-usually requires objective evidence of pathologic process
-objective evidence
often takes the form of, or involves, diagnostic testing
has to tie back to the history, complaints, etc. of the patient (recorded during the initial assessment)
-to have a definitive diagnosis there must be 100% certainty that it is the correct diagnosis
-examples of objective evidence
demonstration of a specific biochemical abnormality
visualization of a tumour by ultrasound imaging
finding an inflamed appendix at surgery
isolation of a bacillus or virus
location of a lesion in the tissue by biopsy
Medical Laboratory Services
-pathology (anatomic)
histology (tissues)
cytology (cells)
-hematology
blood transfusion medicine
immunology
-microbiology
bacteriology
virology
parasitology
mycology (fungus)
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-biochemistry (clinical chemistry)
-genetics
molecular diagnostics
Reasons for Biochemical Testing
-about 70% of medical decisions are based on lab tests
-about 70% of the lab testing done falls under biochemistry (biochemical testing)
-biochemistry analyzes chemical markers found in cells and fluids (like blood, serum, urine, etc.)
-relatively non-invasive and safe
-small sample size/amount is usually enough to perform analysis – dozens of tests can be done on a single
10 cc tube of blood
-many tests (assays) have been developed to a high degree of
sensitivity
accuracy
speed of analysis
-example – high turnover for blood tests (about 30 minutes in a hospital) whereas a biopsy may take days
Objectives of Laboratory Medicine
-diagnosis – help define as objectively as possible health and disease
-prognosis – help predict the course of a disease
-monitoring – monitor the effectiveness of treatment
-etiology – seek the underlying causes of disease
-screening – to screen for unsuspected disease
Use of Biochemical Testing
-using the objectives, examples in biochemistry are
diagnosis – does the glucose level indicate diabetes
prognosis – is the caner curable (predict course)
monitoring – has enough medication been given (test the same thing again and again over time)
etiology – what is the cause of the kidney disease (underlying issue)
screening – what is the risk of having a heart attack in CVD (underlying disease that has already
started by is unaware – cholesterol levels for heart disease)
Societal Role of Laboratories
-mortality and morbidity mean very different things from a disease standpoint
-often the mortality/morbidity rate is measured predicting the course of the disease (prognosis)
-mortality – disease that causes death or reduces life expectancy
-morbidity – disease that impairs the wellbeing of an individual
Worldwide Mortality
-leading causes of death (worldwide)
ischemic heart disease
cerebrovascular disease (stroke)
lower respiratory infections
chronic obstructive lung disease
diarrheal diseases
HIV/AIDS
tuberculosis
cancer of trachea/lung/bronchus
prematurity and low birth weight
diabetes mellitus
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