Testing haemoglobin 

  • There are 2 methods for POC measuring of haemoglobin — non-invasive haemoglobin monitors (eg Masimo Rad or Pronto) and invasive haemoglobinometers (eg HemoCue)
  • Non-invasive haemoglobin (Hb) monitoring is recommended to quickly and accurately check children and adults at risk of anaemia during routine screening and acute illnesses without using blood
  • Most health services now have non-invasive haemoglobin monitors as standard equipment — follow the manufacturers product information for the monitor used at your clinic

Attention

  • Do not use non-invasive monitoring on people with oedema of the fingers (eg kidney disease, pregnancy) — use HemoCue monitor for POC test or do FBC pathology

For non-invasive monitoring (eg Masimo Rad or Pronto)

  • Follow instrument manufacturer's recommendations
  • Place sensor onto the 5th (little) finger of the persons non-dominant hand —  this is the preferred site, other fingers can be used if needed 
  • For children under 10kg place onto big toe, extreme movement can cause inaccurate results — use HemoCue if needed
  • Do not use under bright light (eg direct sunlight or surgical light) — move away from direct light source and cover finger with a cloth when taking measurement if required

For invasive haemoglobinometer (eg HemoCue)

  • Do not do finger prick tests on children under 6 months — use heel instead. For healthy children first routine Hb test is at 6 months
  • Do ask for help from a more experienced practitioner if you are having trouble getting enough blood to do this procedure — you need a full drop of blood for the test to work properly

Figure 5.18  
  • Finger/heel must be very clean and dry, remove nail polish and trim long nail — see Figure 5.18 for correct place to prick
  • Hand or foot needs to have good blood flow —  warm if needed
  • Let blood drop form on its own — do not squeeze
    • Haemoglobinometer reads Hb by colour of blood. If you squeeze to get blood you have extra serum, if skin left wet you have extra water and the reading will be wrong
  • For reliable results use cuvettes from bottle
    • Opened less than 3 months ago. Write use-by date on bottle when you open
    • With lid firmly on. If lid off — throw bottle away

What you need

  • Non-invasive haemoglobin monitor

OR if not available 

  • Lancet
  • Swab and/or warm water to clean finger/heel
  • Calibrated haemoglobinometer 
  • Clean cuvette
  • Clean gauze swab or cotton wool ball
  • Small sticky plaster

What you do

  • Follow manufacturer instructions for non-invasive haemoglobin monitor
  • Check sensor is connected to machine and cable is not twisted or damaged
  • Turn on power and type in persons demographics (HRN and gender) if prompted
  • Press ‘measure SpHb’ button
  • Record reading — note some machines will only display and hold data for 5 minutes
  • Turn off machine and clean with multi-purpose disinfectant wipe or soft damp (not wet) cloth.  Machine does not need sterilising 

OR if not available use haemoglobinometer 

  • If site dirty — wipe with swab and/or clean water and let dry completely
  • Loosely hold finger or heel pointing downward — do not squeeze
  • Prick finger or heel using lancet — let drop of blood form
    • Pressing firmly against skin can give better puncture and blood flow
  • Wipe away first 3 drops of blood
  • Let fourth drop form, put cuvette tip into middle of drop, let cuvette fill by itself — Figure 5.19. Blood will flow easily into collection area

Figure 5.19  
  • If drop not big enough the first time — do not add to it. Start again with different finger or heel
  • Check there are no air bubbles
  • Wipe excess blood off outside of cuvette, quickly put into Hb machine, wait for reading
  • Put firm pressure on puncture site to stop bleeding, put on sticking plaster
  • If screen shows error OR unexpected reading — do test again. May be bubble in blood in cuvette chamber or dirty monitor in machine
    • If still unsure about result — recalibrate machine or take venous blood