Collecting blood samples

Taking blood samples using needles, cuvettes, test strips 

Attention

Vacutainer barrel and needle is the safest way to take blood. This helps prevent needle stick injuries

• You must be in contact with your laboratory to collect samples using the right tube and to store and transport pathology correctly 
• Warm cloth will improve blood flow to needle site
• Do not use cuff or tourniquet for more than 1 minute
• Instead of using tourniquet on small children ask helper to squeeze evenly around limb with hands taking care to avoid any needle stick injury
• If person had mastectomy or fistula — use other side
• Always let skin dry completely after wiping with alcohol

If you don’t have Vacutainer equipment or veins thin or difficult to find — use ordinary 21G needle and syringe or butterfly needle, both are hard to control with wriggling child and you will need help

What you need

• Tourniquet, blood pressure cuff or helper’s hand
• Alcohol wipes
• Vacutainer barrel and needle 
• OR syringe and 21–25G needle
• OR butterfly (scalp vein) needle, 21–25G with screw-top bung
• Blood tubes — type depends on test
• Tray for standing tubes upright
• Slides and holder if making blood slide
• Gauze swab or cotton wool ball
• Small sticking plaster
• Centrifuge for spinning samples (if needed)
• Sharps container

What you do

• If taking more than one sample — follow Table 5.1

4 ways to take blood from vein

1. Using Vacutainer needle and barrel

• Connect needle to barrel — Figure 5.3

• Choose site
• If elbow crease — put arm straight, rest on pillow/table covered with bluey
• Put on tourniquet OR squeeze with helper’s hand OR use adult/paediatric cuff inflated to 80mmHg
• Stretch skin over site, feel for swollen vein. Choose the one that feels biggest — may not be easiest to see
• Clean site with 70% alcohol wipe and let dry
• Use main (dominant) hand. With bevel of needle facing up, push needle in along vein
• When needle in vein, use other hand to steady Vacutainer barrel against skin before putting first blood tube into barrel — Figure 5.4

• Push tube into barrel until grey puncture needle has gone through tube’s rubber stopper. Blood will flow into vacuum sealed tube on its own
• Wait until blood has stopped flowing into tube
• Steady Vacutainer barrel against skin with one hand, take out blood tube with other
• Some blood tubes need mixing straight away so invert tube once and stand up in tray — Figure 5.5 before putting next tube in barrel

• Do this until all tubes have been filled
• Take last tube out of barrel — unless also making a blood slide
• Then undo tourniquet
• Now take needle out of vein
• Put pressure over bleeding site using dry gauze swab or cotton wool ball
• Ask person to press on site. If using arm — keep straight to prevent bruising
• Do not take used needle off a syringe or Vacutainer barrel with your fingers
• Use needle release device if Vacutainer has one — Figure 5.6 and Figure 5.7
• OR use groove at top of sharps container to unwind or pull off needle
• OR put both syringe or barrel and needle straight in to sharps container

• When bleeding from needle site has stopped, put on small sticky plaster or cotton wool ball and paper tape

2. Using butterfly needle

• See butterfly needle

3. Using ordinary needle and syringe

• Connect needle and syringe — size according to vein
• 25G for small children, 21G for adult
• Put needle into vein. See — Using Vacutainer needle and barrel
• Take amount of blood you need to fill blood tubes then undo tourniquet
• Take out needle, put pressure over bleeding site using gauze swab or cotton wool ball, ask person to press on site
• Carefully push needle through rubber stopper of first tube. Blood will flow into tube by itself
• Wait until flow stops, take needle out, invert tube, stand tube upright in tray. Do this until all tubes filled
• When bleeding from needle site stopped, put on small sticky plaster or cotton wool ball and paper tape

4. Using needle only — good for small veins in children or the elderly

• Take rubber stoppers off tubes (be careful not to tip them), stand in tray
• Put needle into vein — Figure 5.8. See — Using Vacutainer needle and barrel
• Let blood drop into tube — Figure 5.9 until you have amount needed

• Undo tourniquet, take out needle and press firmly on site with cotton wool ball
• Put stoppers back into tubes, make sure they are tight, invert tubes, stand tubes upright in tray
• When bleeding from needle site stopped, put on small sticky plaster or cotton wool ball and sticky tape

For all 4 methods

• Make sure all tubes are correctly labelled
• Spin (centrifuge) tubes if needed, put in pathology bag
• Check pathology form/s put in bag with labelled tubes
• Store and transport as needed. Some samples may need to be refrigerated

Common blood tests

Whole blood (eg FBC)

• Use EDTA tubes, usually purple or pink top
• As soon as blood taken, mix well by inverting tube
• Store and transport under refrigeration — try to send same or next day

Serum separated test (eg UEC)

• Use plain/white top or SST/yellow top (gel-filled) tubes
• After collection stand bloods for at least 10 minutes. Bloods need to stand upright first to clot before being spun or may get false results
• Spin (centrifuge) at 4200RPM for 10 minutes until serum completely separated by gel. Properly separated serum/cells in tubes will last up to 1 week if stored correctly
• Store in fridge and transport with ice bricks

Plasma

PTH

• Use special white top PPT tube containing EDTA
• Mix well by inverting tube several times
• If more than 1 day delay getting tube to pathology — spin (centrifuge) tube
• Do not separate or freeze the plasma
• Collect 1 SST tube for calcium testing at the same time — even if not requested

INR

• Use blue sodium citrate tubes
• For test to work properly you must
• Collect right amount of blood — fill to line indicated on tube
• Make sure tube is in date — old tubes are not accurate
• If using butterfly needle —
• First draw blood down empty butterfly tubing using any tube (plain one will do) then discard tube. Otherwise some blood remains in butterfly tubing and you won't collect right amount
• Change to blue top tube
• As soon as blood taken, mix well by inverting tube
• You have 4 hours to get blood to pathology. If any chance of delay — sample must be spun, plasma separated and frozen
• Spin (centrifuge) as soon as you can for 20 minutes
• Lift carefully out of centrifuge so plasma stays separated
• Take tube top off, gently pipette clear yellowy plasma into 5mL plain screw cap tube. Be careful not to collect any red cells. If you do — put plasma back, re-spin
• Freezing and transport — must stay frozen in transit

Blood for testing glucose levels, including OGTT

• Use sodium fluoride–potassium oxalate/grey top tubes
• As soon as blood taken, mix well by inverting tube 6–8 times
• Store and transport under refrigeration 
• Some laboratories require samples to be spun and plasma separated as described above as soon as possible (not frozen) — check with your laboratory

Making a blood slide

What you need

• Pencil and pen
• Clean, dust free glass slide with frosted end
• Another slide to use as spreader
• Slide holder

What you do

• Label slide holder with pen, label frosted end of slide with pencil — Figure 5.10

For thin film

• Need enough blood to make thin 4cm smear
• If using Vacutainer — leave tube on needle as you take it out of arm, drop blood from needle tip onto slide — Figure 5.11

• If using syringe — put drop of blood from needle onto slide before filling tubes
• Holding spreader at 45° angle, gather blood into one spot — Figure 5.12
• Using just one movement, push blood steadily back down slide — Figure 5.13

For thick film (eg malaria parasites)

• Using Vacutainer or syringe put 3 drops of blood on slide — 1 in middle, 1 on either side in a triangle shape — Figure 5.14
• In 1 circular movement, use corner of spreader to join drops up and make round shape about 1cm (10mm) across — Figure 5.15

For both thin and thick smear

• Leave slide to air dry, put into slide holder
• Make sure it is correctly labelled
• Store and transport under refrigeration

Blood cultures

Attention

If collecting blood cultures to send to hospital with person — write in letter/referral, ring hospital to let them know it is coming

• Blood culture bottles for adults may be larger than those for small children, depending on brand — need to stock both
• Store bottle in cool place, less than 25°C (eg pharmacy or fridge)
• On each bottle, check use-by/expiry date, colour of fluid, rubber stopper intact
• Use new, clean needle for each bottle

What you need

• 2 blood culture bottles (10mL or child size), aerobic and anaerobic
• Alcohol swab
• 20mL syringe
• 3 x 21G needles — 1 for taking blood, other 2 for putting blood into 2 bottles
• Artery forceps to take needle off syringe
• Tray for standing bottles upright

What you do

• Take off metal or plastic seals/caps
• Wipe rubber stoppers with alcohol wipe, let dry completely
• Choose injection site, take blood using 20mL syringe and 21G needle
• Take enough blood for both bottles — about 15mL (6–8mL each) for 10mL bottles
• Using forceps or sharps container lid device, carefully take needle off syringe. Don’t contaminate end of syringe. Put needle in sharps container
• Put on new sterile 21G needle, pierce rubber stopper to fill first blood culture bottle. If bottle not vacuum sealed — push blood into bottle gently
• Change needle again, fill second bottle the same way
• Mix well by inverting each bottle, stand upright in tray
• Make sure bottles are correctly labelled
• Store and transport at room temperature — remember to send with person in emergency

Oral glucose tolerance test

75g oral glucose tolerance test (OGTT)

Attention

Remember: People who are acutely unwell (eg have a fever) may show incorrect reading

• Record any medicines person is taking, these may affect test
• Do fasting test in morning. Tell person
• Not to eat or drink anything except water for 8–12 hours before test
• They will have to wait in clinic for 2 hours
• Not to eat or smoke during test — water is OK, but no tea, coffee, snacks
• To rest for 30 minutes before test, keep resting during test

What you need

• Pathology form
• Blood collection equipment
• Calibrated glucose meter
• Pre-mixed solution containing 75g glucose OR 75g Glucose Challenge solution in 300mL water
• 2–3 grey top/sodium fluoride–potassium oxalate tubes, label with time collected and
• Fasting or O hour
• At 1 hour, if needed (eg 24–28 weeks pregnant)
• At 2 hours

What you do

Collecting blood — each time

• Collect blood specimen in tube, add time taken to label
• Put drop of blood from tip of needle on glucose meter testing strip to check blood glucose levels
• On pathology form — record glucose meter BGL test result, note if fasting

Conducting test

• Take first blood specimen in tube labelled 'Fasting' or '0 hour'
• Give person glucose solution to drink in front of you. Should drink it all within 5 minutes
• At 1 hour if needed (eg 24–28 weeks pregnant), take second blood specimen in 'At 1 hour' labelled tube
• Mix well with oxalate by inverting 5–10 times
• At 2 hours, take second/third blood specimen in tube labelled 'At 2 hours'
• Mix well with oxalate by inverting 5–10 times
• Give person a cup of tea and something to eat

Then

• Make sure tubes are correctly labelled
• Store and transport blood tubes under refrigeration