Specimen Collection And Processing

Question 1

Patient’s review comprises:

Answer 1

Good clinical history
Good physical examination
Performing the right laboratory investigation

Question 2

Types of clinical specimens

Answer 2

Blood
Urine
Saliva
Faeces
Cerebrospinal fluid
Tissue fluids such as pleural fluid/aspirates, pericardial fluid, exudates
Swabs for molecular studies such as nasopharyngeal swabs for COVID-19 detection

Question 3

Purpose for adequate specimen collection

Answer 3

To ensure the right specimen is collected for the right testing

To ensure that the laboratory analysis is reflective of the clinical state of the patient

To reduce patient discomfort and ensure safety during and after specimen collection

Question 4

Infection Prevention & control This is to ensure safety for both patients and laboratory personel
Involves the use of personal protective equipment(PPE)
these include?

Answer 4

Laboratory gown
Gloves
Mask
Goggles for eye protection
Alcohol swabs
Plasters

Question 5

Hygiene involves

Answer 5

Ensure proper hand hygiene by use of antiseptic hand rub or washing with soap and water
Infectious patients should be separated from other patients by isolation or by doing a total clean up of the area after sample collection
The specimen collection area must always be kept clean, and sharps disposed appropriately in the sharp boxes
All specimens collected in the clinical laboratory must taken to be potentially infectious and so handled appropriately

Question 6

When making a request for specimen collection

Answer 6

Appropriately filled request form must be tendered. The laboratory personnel must confirm that the form tendered is from the patient the sample is to be collected. Information to be confirmed include
Name
Age
Gender
Hospital number
Make enquiry for history of allergy to latex and alcohol swab
Timing for sample collection
Adequate rest (5 – 10 mins) should be observed before venepuncture

Question 7

Steps in venupencture

Answer 7

Site for venepuncture should be noted- cubital, wrist
Clean the area from inside outward using the right concentration of alcohol swab. Allow the area to air dry
Apply torniquet just above the site to occlude venous flow
Torniquet time should not be greater than one minute to avoid haemoconcentration which can affect analyte like calcium
The venepuncture can be performed using syringe, vacutainer needle or butterfly needle
After bleeding, use dry gauze to stop bleeding

Question 8

Caution during venepuncture

Answer 8

Avoid sites with scars, tattoos, oedema, haematoma, arm with intravenous cannula
Remove needle if any swelling is noted during the process
Limit you number of venous access to one or two trials. You may need to call a more senior medical personnel for assistance
If a patient demonstrates abnormal or alarming clinical scenario, call attention of physician on ground
Do not massage or milk blood to avoid contamination with tissue fluid

Question 9

Heel stick?

Answer 9

Used for newborn screening
Use short length lancet of about 2 mm so as not to injure the calcaneous bone
Collect specimen in microcollection capillary tubes or filter paper for screening or genetic studies
After specimen collection, apply pressure and elevate the foot. Do not apply adhesive bandage

Question 10

Serum is the watery portion of blood that is exuded after blood coagulation in a plain tube. Samples are collected in __________ vacutainer tubes
Serum samples is mostly used for running?

Answer 10

gold coloured capped

Immunoassays

Question 11

Plasma is the non cellular component of anticoagulated blood gotten after centrifugation of the whole sample
Plasma samples can be used for most biochemistry tests in as much as_____________ can be avoided

Answer 11

contamination from ions in anticoagulants

Question 12

Anticoagulants used in clin path lab

Heparin

Answer 12

It is available as lithium heparin and sodium heparin in green capped vacutainer tubes;

Heparin accelerates the action of antithrombin iii and preventing the formation of fibrin
Lithium heparin is used mostly in chemistry lab tests except folate assay

Question 13

EDTA full meaning and use

Answer 13

Ethylenediamine tetra-acetic acid

Mostly used for haematology tests and for DNA studies
Available in lavender capped vacutainer tubes

Question 14

Sodium fluoride

Answer 14

Inhibits enolase enzyme in glycolysis.

It is used for collecting samples for glucose assay and available in grey capped vacutainer tubes

Question 15

Oxalates (Sodium/potassium/Lithium) -

Answer 15

form insoluble complexes with calcium ions.

This is often mixed with fluoride in grey capped vacutainer tubes.

Question 16

Sodium iodoacetate

Answer 16

– inhibits glycolysis

Question 17

Sodium Citrate –

Answer 17

converts calcium to non ionized form; used for coagulation profile testing. Tubes are light blue capped vacutainer tubes

Question 18

Standard tubes in use in Chemistry labs are of 2 types

Answer 18

Vacutainer tubes – These have negative intratubular pressure and are used with vacutainer needles for blood collection. The cap colour codes have been mentioned in earlier slides

2. Ordinary tubes – Much more in use because they are cheaper and readily available
   Lithium heparin – For most biochemistry tests, deep blue coloured capped tube
   EDTA – for haematological test; Green capped tube
   Flouride oxalate – Used for glucose estimation; Yellow capped tube
   Plain tube – No anticoagulant; Red capped tube;

Question 19

Order of draw

This aim to prevent contamination and additive carry over
Blood sample in syringe should be dispensed into sterile tubes, anticoagulant tubes, and then the serum tubes.

Answer 19

The order is as follows:
Sterile tubes
Coagulation study tubes
EDTA tubes
Heparin tubes
Flouride oxalate tube
Serum sample tube

Question 20

Interference in the lab can be as a result of?!

Answer 20

Haemolysis
Icteria
Lipaemia

Interference affects the results generated
Interference can cause falsely elevated or falsely decreased analyte concentration
It is important to avoid or decrease the effect of interference to the barest minimum or request for fresh specimen for analysis

Question 21

Lipaemia

Answer 21

Lipaemia is seen as turbidity in serum or plasma due to presence of excess lipoprotein concentration. Factors that is associated with lipaemia include fatty food intake, altered lipid metabolism, metabolic disorders, lipid infusions
Lipaemia may be visible at serum triglycerider concentration above 300mg/dl
Lipaemic interferences can be reduced by ensuring at least 12 hrs of fasting before sample collection, ultracentrifugation of samples at speed of 10000g

Question 22

Hyper bilribinaemia

Answer 22

Icteric samples result when the concentration of bilirubin is quite elevated. Bilirubin interferes with peroxidase systems used for measurement of glucose, cholesterol. Triglycerides, urea and creatinine. Also, bilirubin interferes with dyes binding to albumin
Running sample blank alongside helps to reduce the effect of spectral bilirubin interferences

Question 23

Hemolysis can be caused by

Answer 23

Using too small-bore needles
Forcing blood through needle
Shaking tube vigorously after blood sample collection and transport
Presence of excess anticoagulant
Centrifuging blood sample before completion of clotting
Freezing and thawing of blood

Question 24

Haemolysis can affect the following analytes during assay –

__________ can help reduce the effect of sample haemolysis

Answer 24

potassium, phosphorus, ALT, acid phosphatase

Sample blanking

Question 25

Specimen handling for analysis : identification

Answer 25

Identification
Name
Lab identification number
Time of sample collection
Note special instruction attached
Handling of all specimens as potentially infectious

Question 26

Specimen handling for analysis
Preservation

Answer 26

Preservation
Transport of specimen in the correct transport medium and temperature
Samples for bilirubin assay should be protected from light to prevent photodegradation
Uncentrifuged samples should not be frozen before separation to avoid sample haemolysis which will act as interference during assay

Question 27

Specimen handling for analysis

Seperation and storage

Answer 27

Separation and storage
Anticoagulated blood samples should be centrifuged for about 15 mins at speed of 2000 to 3000g
Clotted whole blood should be centrifuged after 30 mins at speed of 1500g for about 10 mins
Samples should attain room temperature before start of centrifuging.
Specimen collected should be centrifuged within 2 hours of collection
Serum and plasma should be dispensed into plain tubes unless if collected in serum separating gel tube.
Specimens should be stored at -20°C, If prolonged storage is required, then storage should be at -80°C. Repeated freezing and thawing should be avoided

Question 28

Other biological specimen

Answer 28

Urine –
Random for spot glucose, ketone bodies
Early morning urine
Midstream urine which is best for investigating Kidney/ bladder disorder
Timed specimen which can be for 24hrs for creatinine/ protein assay
Catheter specimen
Suprapubic tap

Question 29

Other specimens

Answer 29

Faeces- occult blood detection, tryptic activity, faecal fat estimation
Tissue fluids – to determine if an effusion or exudate, identification of infectious agent/ cancer cells,
CSF – cell count, glucose, proteins estimation
Saliva – DNA studies, cortisol, blood group
Buccal smears – Essentially for DNA studies