Unit 6: Point-of-Care Testing

• Topic 01

  CLIA-Waived Tests — Glucose, HbA1c, Cholesterol, and INR/PT

  45 questions
• Topic 02

  Glucometer Operation, Calibration, and QC

  39 questions
• Topic 03

  Rapid Strep, Influenza, and COVID Antigen Tests

  46 questions
• Topic 04

  Urine Dipstick and Pregnancy Testing

  45 questions
• Topic 05

  Quality Control Documentation and Corrective Action

  45 questions

A few questions from this unit, with the answer and a full explanation. The complete bank is available when you start practising.

1. A patient's POC HbA1c is 6.3%. The patient asks if they have diabetes. Which response is most accurate?

   • A
     An HbA1c of 6.3% confirms a diabetes diagnosis; any value above 6.0% meets the diagnostic threshold
   • B
     An HbA1c of 6.3% falls in the prediabetes range (5.7–6.4%); diabetes is diagnosed at 6.5% or above, so this result does not confirm diabetes
     Correct answer
   • C
     An HbA1c of 6.3% is borderline; the patient should be told to fast for 24 hours and retest to obtain a definitive answer
   • D
     The phlebotomist should confirm or deny a diabetes diagnosis based on this result and advise the patient accordingly
   Explanation

   An HbA1c of 5.7–6.4% falls in the prediabetes (impaired glycemic regulation) range. A value of 6.5% or above on two confirmed tests is required to diagnose diabetes mellitus. The phlebotomist should report the result to the provider and not independently convey a diagnosis, but can accurately state that the value falls below the diabetes diagnostic threshold.

   Key takeaway: HbA1c 5.7–6.4% = prediabetes; $\geq$ 6.5% = diabetes.

2. A patient's POC HbA1c is reported as 7.8%. The provider asks whether this result reflects the patient's glucose control from the past month only. How should the phlebotomist respond?

   • A
     HbA1c reflects approximately 2–3 months of average glucose control, so one month's glucose behavior accounts for only a portion of the result
     Correct answer
   • B
     HbA1c reflects the past week, meaning the patient has had poor control only recently
   • C
     HbA1c reflects the past six months because hemoglobin is replaced very slowly in adults
   • D
     The phlebotomist should not comment on HbA1c results and should direct all questions to the laboratory director
   Explanation

   HbA1c accumulates over the 2–3 month lifespan of red blood cells. A result of 7.8% therefore integrates glucose levels over roughly the past 90 days, with the most recent weeks contributing more heavily than earlier weeks. A single month accounts for approximately one-third of the measurement window, not the entire result.

   Key takeaway: HbA1c reflects the full 2–3 month window, not just the most recent month.

3. A patient recently received two units of packed red blood cells. Their POC HbA1c is 5.8%. Before the transfusion, their last HbA1c three months ago was 8.4%, and their home glucose log shows consistent readings of 200–280 mg/dL. Which factor most likely explains the current HbA1c result?

   • A
     The 5.8% result is within normal limits and confirms that the patient's previous HbA1c values were laboratory errors
   • B
     Transfused red blood cells are newly formed and not yet glycated, diluting the proportion of glycated hemoglobin and producing a falsely low HbA1c
     Correct answer
   • C
     The POC HbA1c device is not affected by transfusions; the result is reliable
   • D
     Transfusions elevate red blood cell count, increasing total hemoglobin and masking glycated hemoglobin
   Explanation

   Donor red blood cells are newly formed and have not been exposed to the recipient's elevated glucose levels. When transfused, these non-glycated cells dilute the patient's own pool of glycated red blood cells, artificially lowering the HbA1c percentage. This is a well-established interference that must be considered when interpreting HbA1c in recently transfused patients.

   Key takeaway: Blood transfusions dilute glycated hemoglobin with non-glycated donor cells, producing a falsely low HbA1c.