clinical biochemistry sheet1

question

the function of the clinical lab is
answer

to perform qualitative and quantitative analysis on body fluids such as blood, urine,and spinal fluid, as well as feces,tissue,calculi and other material
question

Biochemical results are useful for
answer

diagnosis and treatment of disease
question

Biochemical tests are used in
answer

diagnosis -prognosis -monitoring -screening
question

Diagnosis:
answer

art or act of distinguishing one disease from another
question

Medical diagnosis is based on
answer

the patient‟s history combined with the findings on examination.
question

a differential diagnosis
answer

making a correct decision between diseases presenting a similar clinical picture
question

Biochemical tests are important for
answer

confirmation or rejection of clinical diagnosis
question

Prognosis:
answer

medical term indicates the doctor’s prediction of how a patient’s disease will progress, and whether there is chance of recovery
question

based on what the prognosis
answer

knowledge of the course of the disease in other patients together with the general health, age and sex of the patient
question

serial measurements of plasma creatinine concentration in progressive renal disease are used to indicate when dialysis may be required example on what?
answer

Tests used primarily for diagnosis may also provide prognostic information
question

major use of biochemical tests
answer

1- follow the course of an illness 2- monitor the effects of a treatment
question

Monitoring (sequential recording, keep watch over)
answer

there should be a suitable analyte, for instance, glucose in patients with diabetes mellitus
question

In clinical chemistry, most measurements are concerned with the concentrations of substances
answer

in solutions, the solutions most often being blood, serum,urine, spinal fluid, or other body fluid. The substance that is dissolved in a solution is a solute or analytes.
question

Biochemical tests may also be used to detect complications of treatment, such as
answer

hypokalemia during treatment of diuretics
question

Screening (examine for the presence or absence of a disease)
answer

to determine Subclinical diseases: An illness that stays below the surface of clinical detection, which has no recognizable clinical findings .
question

the best known example of screening is
answer

mass screening of all new born babies for phenylketonuria, which is carried out in many countries.
question

The clinical biochemistry tests can be divided into three main category
answer

1- Core biochemistry 2- Specialized tests 3- The emergency lab
question

Core biochemistry
answer

are the commonly requested tests which are of value in many patients, on frequent basis.
question

Specialized tests
answer

Not every lab is equipped to carry out all possible biochemistry requests. Less commonly asked tests for.
question

The emergency lab
answer

All clinical biochemistry labs provide facilities for urgent tests. Only a small number of test types are available from the emergency lab. These tests are processed rapidly. An urgent test is designed as test on which the clinician is likely to take immediate action.
question

Core biochemical tests
answer

Sodium, potassium, chloride and bicarbonate Urea and creatinine Calcium and phosphate Total protein and albumin Bilirubin and alkaline phosphatase ALT and AST-glutamyl transpeptidase Creatinine kinase H+, PCO2, and PO2(blood gases) GlucoseAmylase
question

Specialized tests
answer

Hormones Specific proteins Trace elements Vitamins Drugs Lipids and lipoproteins DNA analysis
question

Emergency tests
answer

Urea and electrolytes Blood gases Amylase Glucose Salicylates Paracetamol Calcium
question

major specimens analyzed
answer

Blood • Urine • Cerebrospinal Fluid
question

Choice of specimen type depends on
answer

– Analyte to be measured – Ease of collection
question

Source of blood
answer

– Veins – Arteries – Skin puncture-capillary blood
question

Collection Method of blood
answer

– Syringe – Evacuated tube • Additives • Separator gel – Intravenous lines
question

Factors affecting choice of Blood Source and Collection Method
answer

– Analyte under investigation – Patient • vascular status • ease of collection
question

__________ s usually the specimen of choice
answer

Venous blood
question

Skin puncture
answer

only a small volume of blood is required for a blood test (e.g., a blood glucose test)
question

• A skin puncture may be used to obtain the sample in
answer

an infant younger than 1 year, the lateral or medial plantar surface of the foot should be used for skin puncture
question

Whole blood needed for testing
answer

anticoagulant must be added to the specimen during the collection procedure. Whole blood is rarely required for clinical chemistry tests; only for blood gas, ammonia, and some trace element determinations
question

Plasma needed for testing
answer

Plasma is the fluid fraction of blood. If plasma is desired for testing, an anticoagulant must be added to the specimen during the collection procedure
question

Serum needed for testing
answer

Serum is the supernatant fluid which forms when blood clots
question

plasma
answer

Plasma is fluid component of blood. Comprises ~55% of total volume ofwhole blood. Contains proteins, sugars, vitamins,minerals, lipids, lipoproteins And clotting factors. 95% of plasma is water
question

If blood is collected and allowed to stand it will clot. Formation of an insoluble fibrin clot. If blood is then centrifuged the fluid portion is known as
answer

SERUM
question

If blood is collected into a plain tube and allowed to clot after centrifugation what it will produce?
answer

serum specimen is obtained
question

Serum from coagulated blood is the specimen of choice for many assay systems, but plasma
answer

obtained with an appropriate anticoagulant may be an equally valid specimen.
question

The use of plasma accelerates
answer

analysis in medical emergencies and when the analyte is unstable.
question

why not serum for emergency?
answer

Because serum requires a wait of 15 to 30 min for coagulation
question

Plasma yield from a given volume of whole blood is _______ than the yield of serum
answer

is always greater (15 to 20 % more in volume of plasma than of serum can be isolated from the same volume of blood).
question

The formation of fibrin clots or fragments when plasma is stored and the subsequent risk of
answer

blockage sample probes of automated analytical instruments is a disadvantage
question

Plasma is also not suitable for
answer

electrophoretic analysis, because the presence of fibrinogen can confuse interpretation of electrophoretic patterns
question

Blood specimen tubes for specific biochemical tests like?
answer

Serum separator tube (SST) contains a gel at the bottom to separate serum
question

The type of urine to be collected is determined by
answer

the tests to be performed.
question

the most concentrated specimen and thus is preferred for microscopic examinations.
answer

clean, early-morning, fasting specimen
question

It is satisfactory in most cases to use specimen collected with
answer

careful attention to cleanliness and to keeping the urine cool.
question

Collection of urine is preferred to be
answer

fresh, no need for preservatives. But 24 hour urine sample, must introduce a preservative.
question

The most common preservatives in urine collection
answer

freeze, glacial acetic acid nitric acid
question

Preservatives have different roles but are usually added to
answer

reduce bacterial action or chemical decomposition or to solubilize constituents that might otherwise precipitate out of solution
question

Collection of faeces
answer

to detect the presence of “hidden” or so called occult blood, which is recognized as one of the most effective evidences to the presence of bleeding ulcer or a malignant disease in the GIT
question

Collection of spinal fluid
answer

Spinal fluid is normally obtained from the lumbar region. Spinal fluid is examined when there is a question as to the presence of meningitis
question

Synovial fluid aspiration
answer

synovial fluid is withdrawn from joints to aid characterization of the type of arthritis and to differentiate non-inflammatory from
question

SAMPLING ERRORS
answer

There are a number of potential errors which may contribute to the success or failure of the laboratory
question

Blood Sampling technique
answer

Difficulty in obtaining a blood specimen may lead to haemolysis with consequent release of potassium and other red cell constituents. Results of these tests will be falsely elevated.
question

Prolonged stasis during vein puncture:
answer

Plasma water diffuses into the interstitial space and the serum or plasma sample obtained will be concentrated. Proteins and protein-bound components of plasma such as calcium or thyroxine will be falsely elevated.
question

Insufficient specimen:
answer

analysis requires certain volume of specimen to enable the test to be carried out
question

Error in timing:
answer

The biggest source of error in the measurement of any analyte in a 24-hour urine specimen is in collection of an accurately timed volume of urine.
question

•Incorrect specimen container:
answer

for each blood sample, the correct container with the proper anticoagulant should be used
question

Samples for glucose
answer

should be collected into a special container containing fluoride which inhibits glycolysis
question

If a sample is collected into the wrong container
answer

it should never be decanted into another type of tube. For example, blood which has been exposed to EDTA (an anti-coagulant used in sample containers reduced calcium concentration approaching zero.
question

•Inappropriate sampling site:
answer

Blood samples should not be taken ‘downstream„ from an intravenous drip. e.g Blood sample for glucose taken from the same arm into which 5%, glucose is being infused.
question

•Incorrect specimen storage
answer

A blood sample stored long time before analysis show falsely high potassium, phosphate and RBC enzymes as lactate dehydrogenase
question

Biochemical test results are usually compared to a
answer

reference range considered to represent the normal healthy state
question

Most reference ranges are chosen randomly to include
answer

95% of the values found in healthy volunteers by definition 5%, of the population will have a result out of reference range.
question

no rigid limits to separate the diseased population from the healthy. T OR F
answer

T
question

Biological factors affecting the interpretation of results
answer

• Sex of the patient. • Age of the patient. • Effect of diet. • Time when sample was taken. • Stress and anxiety. • Posture of the patient. • Effects of exercise. • Medical history. • Pregnancy. • Drug history.
question

Time when sample was taken:
answer

• Many constituents of body fluids exhibit cyclical variations (Circadian variation); throughout the day: occurring in 24-hour periods. • These cyclical variations may be quite large the drawing of specimen must be strictly controlled. • The concentration of serum iron, may change by as much as 50% from 08:0 to 14:0 hours, and that of cortisol may change by a similar amount between 08:0 and 16:0.
question

Posture of the patient.
answer

• The blood volume of an adult in an upright position is typically 600 to 700 ml less than that of an adult in lying down position. • Changes from a lying to an upright position associates to reduction of about 10% in the blood volume.
question

Posture of the patient. (2)
answer

• Fluid reduction in plasma is associated with a comparable increase in the plasma protein concentration. • The concentrations of all proteins, including enzymes and protein hormones, and of such compounds as drugs, calcium and billirubin, which circulates partly bound to protein, are also affected.
question

Sodium
answer

135-145 mmol/L
question

Potassium
answer

3.5-5.0 mmol/L
question

Calcium
answer

2.2-2.6 mmol/L
question

Phosphate
answer

0.8-1.4 mmol/L
question

Glucose
answer

2.8-6.0 mmol/L
question

Urea
answer

3.3-6.7 mmol/L
question

Creatinine
answer

60-120 mol/L
question

Albumin
answer

30-50g/L
question

Total protein
answer

60-80 g/L
question

Bilirubin
answer

3-20 mol/L
question

AST
answer

10-50 IU/L
question

ALP
answer

30-150 IU/L
question

GGT
answer

0-60 IU/L
question

Total cholesterol
answer

140-200 mg/dl
question

HDL cholesterol
answer

29-60 mg/dl

Get instant access to
all materials

Become a Member