Preanalytical Variables–Critical for Appropriate Diagnosis

The laboratory total testing process begins with the preanalytical phase and concludes with the postanalytical phase.  Due to improvements in analytical techniques and effective quality programs, most errors now occur in the pre- and postanalytical phases, areas that laboratory professionals sometimes perceive as being ‘out of our control’.

Laboratory errors may be associated with inappropriate patient care in 6.3-24.4% of cases ¹.  Of those errors, up to 73% may be preventable².

The highest incidence of laboratory errors occurs in the preanalytical phase. ^1,3.  Preanalytical errors may not only impact on patient care and contribute to incorrect diagnosis, they may also contribute to increased healthcare costs.  Preanalytical errors may contribute 0.023-1.2% of total hospital operating costs⁴.  Preanalytical variables include those related to the patient, specimen collection and specimen handling.  “Patient variables include:  age, body mass, gender, race, diet, medications, smoking, pregnancy, exercise, dehydration”.⁵  “Specimen collection variables include anticoagulants, order of draw, capillary versus venous specimen, posture, time of collection, diurnal variation, fasting status, length of time for tourniquet placement, and presence of IV’s”.⁵  “Specimen handling variable include labeling, transport conditions, processing time, centrifugation, aliquoting, sunlight, hemolysis, lipemia, temperature and  evaporation”.⁵

This case study demonstrates how preanalytical variables can negatively affect a quality outcome, increase the cost of care, and lead to potential diagnostic errors.

Case Study:

• 67-year-old male patient with long term diagnoses of: type 2 diabetes mellitus, essential hypertension, mixed hyperlipidemia; all of which were in control through medication
• Patient acquired an influenza type infection which resolved but patient clinical status deteriorated leading to increased shortness of breath on exertion, fatigue, and was incapable of completing daily routines.
• Patient was seen in clinic for worsening symptoms, diagnosed with atrial fibrillation with rapid ventricular rate, and admitted to a specialty heart hospital in acute heart failure identified with an echocardiogram with contrast media demonstrating only 25% (severe decrease) left ventricular ejection fraction.
• During his 6-day hospitalization he was diuresed of approximately 20 pounds of fluid, underwent successful external cardioversion and discharged to home with appropriate medications and a defibrillator life vest due to his heart failure status.
• For the next 3 months the patient continued to wear the defibrillator life vest.  His care was followed with clinic visits and laboratory testing.  He was stable and did not demonstrate symptoms of worsening heart failure.
• An echocardiogram with contrast media was performed to assess status four months after discharge from the hospital along with additional laboratory testing including BUN and creatinine.
• Echocardiogram results showed significant improvement in left ventricular function.
• The day after his laboratory tests were analyzed, the patient received an alarming call from his physician describing his concern about his kidney function and that he may need to see a nephrologist.
  • Laboratory results:         BUN 24 mg/dL (normal); Creatinine 2.5 mg/dL (high)
  • 1-month prior results:   BUN 23 mg/dL (normal); Creatinine 1.1 mg/dL (normal)
  • 2-month prior results:   BUN 23 mg/dL (normal); Creatinine 1.0 mg/dL (normal)
• Further review was completed and identified:
  • His specimen for laboratory testing was collected immediately after the echocardiogram was completed.
  • It was noted that the contrast medium used in procedure should not have caused the elevation of the Creatinine but with patient’s underlying diagnosis’ it could not be ruled out as a contributing factor.
  • Repeat BUN and Creatinine was ordered 2 days later and test results were back to normal.

Areas of concern related to this case include:

• Interfering substance: the laboratory specimen was collected after the echocardiogram procedure which required the use of contrast media
• The patient was not asked about any potential pre-analytical variable, such as recent imaging procedures, diet, etc.; information that would have either prevented the collection of the specimen at that time or a notification on the laboratory test report could have been included to assist the physician with interpretation.
• The patient underwent emotional distress after receiving news that he may have an additional condition–kidney disease. Without reviewing the previous laboratory test results and repeat testing, this near-miss was a potential misdiagnosis and incurred an increased cost of care due to the repeat laboratory testing.

This case study demonstrates how preanalytical variables influence laboratory test results that can cause diagnostic error that impact safe patient care.  As essential members of the healthcare team, laboratory professionals must be empowered to do what is right to prevent errors.  Even though they may not be in direct control of all preanalytical processes, they can collaborate with physicians and other healthcare professionals to focus on preventing errors.

References:

1. Zemlin AE. Errors in the Extra-Analytical Phases of Clinical Chemistry Laboratory Testing.  Division of Chemical Pathology, National Health Laboratory Service, Cape Town, South Africa.  Published online:  05 May 2017 Ind J Clin Biochem
2. Carraro P, Plebani M. Errors in a stat laboratory: types and frequencies, 10 year later. Clin Chem. 2007; 53:1338-42
3. Lippi G, Chance JJ, Church S, Dazzi P, Fontana R, Giavariana D, et al. Preanalytical quality improvement; from dream to reality. Clin Chem Lab Med. 2011; 49:1113-26
4. Green SF. The cost of poor blood specimen quality and errors in preanalytical processes. Clin Biochem.  2013;46: 1175-9.
5. Plumhoff EA, Masoner D, Dale JD. Preanalytic laboratory errors: identification and prevention.  Mayo Clin Commun.  2008; 33:1-8.