NHA CPT common mistakes
NHA CPT · Understand the traps and how to avoid them.
Reciting the order of draw from memory as needle, syringe, then tubes, and placing the light-blue sodium citrate tube after the serum tube because it 'looks like it should go with the other blue-top tube.'
Candidates memorise a mnemonic but never anchor it to the additive chemistry, so under exam pressure they reorder tubes by colour similarity or by habit from their training site. The order exists to prevent additive carryover: clot activators and silica from serum tubes can shorten clotting times in citrate tubes, and EDTA carryover chelates calcium in subsequent tubes.
What to do instead
Memorise the order by additive class, not colour: blood culture bottles, then sodium citrate (light blue), serum tube with or without clot activator or gel (red, gold, speckled), heparin (green), EDTA (lavender/pink), then sodium fluoride/potassium oxalate (grey). Rehearse by writing the additive next to each colour and explaining to yourself why each position prevents carryover. Expect at least one question that swaps a tube to test the reasoning, not the list.
On a capillary draw, wiping away the first drop of blood and then filling a lavender microtainer by milking the finger hard with repeated squeezing.
Candidates learn 'wipe the first drop' as a ritual without connecting it to tissue fluid dilution, and they squeeze because the drop is slow. Hemolysis and tissue-fluid contamination distort potassium, LDH, and glucose results, and excessive squeezing is the most common cause of a rejected capillary specimen.
What to do instead
Wipe the first drop, then let blood well up with a gentle intermittent pressure from the proximal phalanx, releasing between pulses. If flow is poor, warm the site or choose a different finger rather than increasing pressure. Remember the exam links 'milking' to hemolysis and tissue-fluid contamination, not to speed.
Identifying a patient by asking 'Are you Mr. Smith?' and accepting a nod, or relying on the room number or wristband alone without a verbal confirmation of two identifiers.
This is a habit carried from busy clinical settings where confirmation is implied, and candidates underestimate how often the exam tests the two-identifier rule as a discrete item. The Joint Commission and CLSI standard require two independent identifiers, and a yes/no question invites misidentification of a confused or sedated patient.
What to do instead
State the rule as an action: ask the patient to state and spell their full name and give their date of birth, then compare both to the requisition and the wristband. For a patient who cannot speak, a family member or caregiver may confirm, but the wristband and requisition must still be matched. Practise phrasing it as an open question, not a yes/no prompt.
Choosing the median cubital vein by default even when it is not palpable, then probing with the needle tip under the skin to 'find' it.
Textbook diagrams make the antecubital veins look uniform, so candidates treat the first-choice site as mandatory. Probing causes hematoma, arterial puncture, and nerve injury, and the exam tests site selection criteria such as scarring, fistulas, mastectomy side, and IV lines.
What to do instead
Palpate before you choose. Use the median cubital first only if it is bouncy and fixed; otherwise step to the cephalic or basilic. Avoid the arm on the side of a mastectomy with lymph node dissection, an active fistula or vascular access device, or an area with hematoma, scarring, or edema. If no site is suitable after a reasonable attempt, stop and seek another collector rather than probing.
Reaching for a tourniquet and needle before checking for anticoagulant therapy, latex allergy, or a history of fainting, and applying the tourniquet for well over a minute while organising supplies.
Candidates treat patient assessment as paperwork separate from the draw, and they tie the tourniquet early so they can arrange tubes. Prolonged tourniquet time concentrates proteins and potassium and alters results, and skipping allergy and bleeding history creates preventable harm.
What to do instead
Sequence it deliberately: confirm identity, then ask about anticoagulants, latex allergy, prior fainting, and any fistula or IV site, then select the site and apply the tourniquet. Keep tourniquet time under one minute; release it as soon as blood flow is established if the tube allows. If the patient reports fainting, draw supine or with a companion present.
Filling a tube to the top by pushing the plunger of a syringe or by squeezing blood from a syringe into a coagulation tube, and using a 23-gauge butterfly for a light-blue tube on a small vein.
Candidates focus on getting enough blood rather than on the additive-to-blood ratio, and they do not connect needle gauge or syringe transfer to hemolysis and short draws. Underfilled citrate tubes and shear stress from a small needle both produce falsely prolonged clotting times.
What to do instead
Let vacuum fill the tube to the marked line; never top off a short draw. For syringe draws, discard the needle and transfer gently through the syringe hub into the tube, letting the vacuum pull the blood. Use a 21-gauge or larger needle for coagulation testing when the vein permits; if a butterfly is required, use one with a discard tube or a winged set designed for the purpose.
Labelling tubes at the desk after leaving the bedside, or pre-labelling empty tubes before the draw.
Candidates batch-label to save time, especially when drawing several patients. Pre-labelling and delayed labelling are the leading causes of wrong-blood-in-tube events, and the exam treats labelling as part of the collection event, not an after-the-fact task.
What to do instead
Label each tube at the patient's side, immediately after filling, before capping or placing it in the tray. Confirm the label against the requisition and the patient's stated identifiers. If a tube is found unlabelled later, do not label it; discard and recollect.
Centrifuging a serum separator tube immediately after collection, or spinning a light-blue tube at the same speed and time as a chemistry tube.
Candidates apply one centrifugation setting to every tube because the centrifuge has a single default, and they forget that serum needs complete clot formation first. Spinning serum before clotting finishes produces fibrin strands and a poor barrier; under-centrifuged citrate plasma retains platelets that falsely lower clotting times.
What to do instead
Let serum tubes clot fully, typically 30 minutes at room temperature, before centrifugation. Follow the tube manufacturer's g-forces and times: citrate tubes generally require higher g-force and longer time than plain chemistry tubes because platelet-poor plasma is the goal. Balance the centrifuge, cap tubes appropriately, and record the spin conditions if the protocol requires it.
Transporting a light-blue tube on ice with the rest of the chilled specimens, or leaving a urine sample and an ammonia specimen at room temperature in the same rack.
Candidates generalise 'keep specimens cold' or 'keep specimens warm' as a single rule. Chilling citrate tubes activates cold-dependent factors and falsely shortens clotting times, while ammonia and some urine analytes require chilling or specific preservation, so a single rack temperature cannot serve both.
What to do instead
Group specimens by transport requirement before leaving the patient: room-temperature coagulation tubes, chilled ammonia and blood gas specimens, protected-from-light bilirubin, and urine according to the test. Read the handling requirement as part of the order, not as an afterthought, and use a separate transport bag or rack for chilled specimens.
Handling a needlestick by squeezing the site, applying alcohol, and continuing the draw before reporting it, or recapping a needle with two hands because the sharps container is across the room.
Candidates freeze after an injury and default to first-aid habits, and they recap to avoid carrying an exposed needle. Squeezing does not remove contaminated blood and can damage tissue; two-handed recapping is the classic cause of needlesticks, and delayed reporting forfeits post-exposure prophylaxis timing.
What to do instead
For a needlestick: stop, wash the site with soap and water, do not squeeze or scrub, and report immediately to the designated supervisor so exposure evaluation and prophylaxis can begin. For prevention, never recap with two hands; use a one-handed scoop method only if no safety device exists, activate the safety engineered device, and dispose at the point of use in a sharps container filled no more than three-quarters.