Chem Path Test Revision Flashcards
Chemical pathology?
Is a branch of pathology that deals with the biochemical analysis of biological specimen for assessment of disorders
Describe atrial blood collection
An arterial blood sample is collected from an artery, primarily to determine arterial blood gases.
The sample can be obtained either through a catheter placed in an artery, or by using a needle and syringe to puncture an artery. These syringes are pre-heparinized and handled to minimize air exposure that will alter the blood gas values.
Glass is preferred to plastic because glass is impermeable to gases while plastic is permeable.
Pco2 changes are insignificant if stored in ice. Therefore, changes are minimized by transporting specimen in ice until utilized.
Heparin concentration should be kept low because high concentrations will the PH, HCO3, base excess and calcium.
•Glass activates the coagulation factors & platelets more rapidly than plastic does, glass therefore requires more Heparin.
Collection of saliva
May be used as alternative to blood in neonates or infants
•Analysis of hormones & drugs;
•Free cortisol, progesterone, oestradiol, 17 - OH- progesterone, testosterone
•Drugs: pcm, caffeine, diazepam, ethanol, theophylline & digoxin.
•Describe the procedures for conclusion
•If specimen is viscous, freeze to eliminate froth & denature mucin.
•Thaw 4 centrifuge
•Do not brush teeth at least within 3hrs before collection. suck with syringe
Collection of feaces
Stool specimen collection is the process of obtaining a sample of a patient’s feces for diagnosic purposes.
Purpose
This procedure is used to test for infectious organisms, mucus, fat, parasites, or blood in the stool.
Precautions
Depending on the proposed analysis of the feces, watery feces will not be suitable for conducting a test for any fat that may be present, but can be used for other analyses, such as testing for bacteria.
Description
A stool specimen or culture can also be called a fecal specimen or culture. A specimen of freshly passed feces of 0.5 to 1 ounce (15 g to 30 g) is collected, without contamination of urine or toilet tissue, into a small container that may have a small spoon or spatula attached inside the lid of the cup for easier collection of the sample.
Adult and older children patients can collect the specimen by passing feces into plastic wrap stretched loosely over the toilet bowl. A portion of the sample is then transferred into the supplied container.
With young children and infants wearing diapers, the diaper should be lined with plastic wrap. A urine bag can be attached to the child to ensure that the stool specimen is not contaminated with urine.
For a bedridden patient, the specimen should be collected in a bedpan lined with plastic wrap, and the nurse can transfer a portion of the feces into the appropriate container.
Follow the manufacturer’s guidelines if a commercial collection kit is used.
Preparation
If occult blood is suspected, the patient should be given a mild laxative and should avoid eating foods rich in meat extracts or leafy vegetables three days prior to the test. If the patient’s gums bleed when brushing their teeth, the mouth should be cleansed with mouthwash and wiped with a cloth to avoid blood entering the digestive system and contaminating the stool specimen.
Certain drugs may interfere with the analysis of the specimen, and the patient should avoid ingesting products such as antacids, oily foods and drugs, and antibiotics. Barium sulfate should be excluded two weeks prior to the test, and medical procedure dyes three weeks prior to the test.
If fat in the stool is suspected, the patient will also be asked to collect the samples in pre-weighed airtight containers.
All feces passed in a 24-hour period are collected over two or three days and sent daily for analysis.
Aftercare
The patient should be made clean and comfortable.
All contents of kits, towels, plastic wrap, gloves, and bedpans should be disposed of in appropriate containers. The nurse should wash and dry his or her hands thoroughly.
Speed in testing the sample is essential, in order that an accurate result is obtained. Therefore the specimen should be sent for testing as quickly as possible.
Complications
If there is a delay in sending the specimen for testing, organisms present in the feces may die, while others may multiply, giving a false reading.
Patients should inform medical staff of any medications currently being taken as elements of the drugs may be present in the feces.
Results
The specimens are compared with normal values. Abnormal results indicate that infection, disease, or parasite infestation are present.
Health care team roles
The nurse should be aware of the qualities of normal feces, and note if the patient has any difficulties in passing feces. As many patients may feel uncomfortable performing this collection properly, the nurse should also educate the patient concerning the reasons for having it done.
Fecal occult blood test
Used to check for presence of blood in stool
Old/brown blood
* blood can be seen with naked eye
Frank blood test
Fresh blood
Collection of csf
A cerebrospinal fluid (CSF) culture is a laboratory test to look for bacteria, fungi, and viruses in the fluid that moves in the space around the spinal cord. CSF protects the brain and spinal cord from injury.
A sample of CSF is needed. This is usually done with a lumbar puncture (also known as a spinal tap).
The sample is sent to the laboratory. There, it is placed in a dish that has a special substance called a culture medium. Laboratory staff then observe if bacteria, fungi, or viruses grow in the dish. Growth means there is an infection.
Interpretation of biochemical results
The laboratory result must be interpreted on the background of a reference interval that is used to distinguish between “health” and “disease”. The clinician must also evaluate the result from the knowledge of biological variation and be aware of the potential risk of false interpretation.
•The laboratory test request is usually requested to confirm or rule out empirical diagnoses made on the basis of patient’s clinical condition.
•If the laboratory test result does not fit into the patient’s clinical condition,then the possibility of an error should be investigated.
•If there is no error after investigation, the patients sign and symptoms should be re-evaluated.If it is still not correlating with the clinical conditions,further assessment should be made by:
•Considering the pattern of abnormalities e.g Hyperkalemia associated with hyponatremia can indicate Addison diseases, potassium sparing diuretic or diabetic acidosis
Reference interval
A reference interval is a statistically derived set of figures which indicates the range of values for a given analyte, found in the majority(95%) of the population.
Reference interval – spans the limits of results expected for a defined healthy population
•This defines a specific percentage of the population (usually 95%) – a percentage (5%) will fall outside the reference interval in the absence of disease.
•All “Normal ranges” are Reference intervals, but not all Reference intervals are normal ranges e.g., Reference interval for therapeutic drug levels is not a Normal range since normal people are not on drugs
Factors that influence reference interval
Age-
–Alkaline Phosphate(ALP) is high in infants,children and young adults(upper limit up to 2.5 times of adult level)
–Plasma phosphate-high in infants and children
•Sex
–Plasma gamma glutamyl transferase(GGT)-Lower in women(male≤45U/Female<30U/L)
–Plasma testosterone-lower in women;plasma urate-lower in women
•Physical size-
–Plasma creatinine is lower in infants,children and small women(since creatinine level is directly proportional to muscle mass)
•Pregnancy
–Alkaline phosphatase higher in third trimester of pregnancy
•Time of sampling
–plasma cortisol exhibits circadian rhythm –higher in the morning
–Oestradiol varies with
Ethnic
–Plasma creatinine kinase may be higher in black than in white people.
–Enzymes are not usually expressed in moles but as enzyme activity in
Units - enzyme units
Large molecules such as proteins are reported as
Grams/milligrams
Blood gas results (PCO2 or PO2) are expressed in
kilopascals (kPa) or millimeter of mercury (mmHg), the units in which partial pressures are measured.
Reference interval
Range or interval of values that is considered normal for physiological measurement in a healthy person
