This document discusses laboratory errors in medical practice. It notes that 0.1-3% of laboratory tests have errors, with most occurring in the pre-analytic and post-analytic phases rather than the analytic phase. Common pre-analytic errors include inappropriate test requests, order entry mistakes, misidentification of patients, and improper sample collection, transport, or storage. Analytic errors are less than 10% of total errors. The document also provides examples of how biological and behavioral factors can influence test results, and discusses clinical performance characteristics of medical tests.

1. Laboratory Errors in
Medical Practice
Mohammad Tanvir Islam
Assistant Professor , Medicine
Bangabandhu Sheikh Mujib Medical University

2. “Anyone who has never made a mistake has
never tried anything new.”

3. “Smart people learn from their mistakes.
But the real sharp ones
learn from the mistakes of others.”
Brandon Mull

5. Why did the TITANIC sink?

6. Laboratory Testing Cycle
Pre-Analytic phase
Ordering a test
Order transferred to lab
Identifying information entered
Specimen obtained
Post analytic phase
Report generated
Result conveyed to clinician
Analytic phase
Data interpreted Specimen analyzed
Clinical response to result

7. • 0.10- 3.0%
• Mostly pre-analytic and post-analytic
• Analytic mistakes are <10% of all errors

8. Pre-Analytic
• Inappropriate test request 46%-68.2%
• Order entry errors
• Misidentification of patient
• Container inappropriate
• Sample collection and transport inadequate
• Inadequate sample/anticoagulant volume
ratio
• Insufficient sample volume
• Sorting and routing errors
• Labeling errors

9. Questions to ask Before ordering a Test
• Why is the test being ordered
• What are the consequences of not
ordering the test
• How good is the test in discriminating
between Health versus Disease
• How are the test results interpreted
• How test results influence Mx & outcome

10. Clinical Performance
Characteristics
• Prevalence
• Sensitivity
• Specificity
• Efficiency
• Positive Predictive Value
• Negative Predictive Value

11. • In useful test sensitivity+specificity should be>170
• Prevalence of a disease can affect the PPV /NPV
• Cutoff value of a test can change the sensitivity &
specificity

12. Shotgun versus Rifle

13. Common Causes of Pre-analytical
Error
Biological
• Age Diseases:
• Sex • Hypothyroidism
• Race (Blacks vs. Caucasians) • Nephrotic syndrome/chronic
renal failure
Timing of test • Biliary tract obstruction
Behavioral Drug Therapy:
• Diet • Amiodaron – on thyroid profile
• Obesity • Diuretics –on pleural fluid
• Smoking • Propanolol
• Alcohol intake • Oral contraceptives
• Caffeine intake • Prednisolone-on immune
• Exercise markers
• Stress

14. Timing of test
• Hepatitis virus
• Dengue serology
• Cardiac enzymes
• Pencreatic enzymes
• Widal test

15. • Pregnancy
• Specimen Collection & Handling
– Specimen obtained from wrong patient*
– Specimen mix-up*
– Nonfasting vs. fasting (12 h)
• Anticoagulant:
– EDTA
– Heparin
• Capillary vs. venous blood
• Hemoconcentration (eg, use of a tourniquet)
• Specimen storage (@ 0–4 C for up to 4 days)

16. Non-specific laboratory abnormalities in
thyroid dysfunction
Thyrotoxicosis
Serum enzymes
– Raised alanine aminotransferase, γ-glutamyl transferase (GGT), and
alkaline phosphatase from liver and bone
• Raised bilirubin
• Mild hypercalcaemia
• Glycosuria
– Associated diabetes mellitus
– 'Lag storage' glycosuria
Hypothyroidism
Serum enzymes
– Raised creatine kinase, aspartate aminotransferase, lactate dehydrogenase
(LDH)
• Hypercholesterolaemia
• Anaemia
– Normochromic normocytic or macrocytic
• Hyponatraemia

17. Analytic
• Equipment malfunction 7%-13%
• Sample mix-ups/interference
• Undetected failure in quality control
• Procedure not followed
• Can be RANDOM or SYSTEMIC

18. Post-Analytic
• Failure in reporting 18.5%-47%
• Erroneous validation of analytical data
• Improper data entry

19. •This was Captain E. J. Smith's retirement trip. All he had to do was get to New York in record time
•Captain Smith ignored seven iceberg warnings from his crew and other ships
•If he had called for the ship to slow down then maybe the Titanic disaster would not have happened

20. •About three million rivets were used to hold the sections of the Titanic together
•They were made of sub-standard iron

21. Bruice Ismay
•Wanted to show that they could make a six-day crossing
•To meet this schedule the Titanic could not afford to slow down
•It is believed that Ismay put pressure on Captain Smith to maintain
the speed of the ship

22. 1. Titanic had sixteen watertight compartments.
2. Compartments did not reach as high as they should have done.
3. The White Star Line did not want them to go all the way up because
this would have reduced living space in first class.
4. If Mr Andrews, the ship's architect, had insisted on making them the
correct height then maybe the Titanic would not have sunk.

23. The final iceberg warning sent to Titanic
was from the Californian.
Captained by Stanley Lord, she had
stopped for the night about 19 miles north
of Titanic.
At around 11.15, Californian's radio
operator turned off the radio and went to
bed.

24. • “Good judgment comes from experience,
and experience comes from bad
judgment.”
― Rita Mae Brown
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