Laboratory errors in medical practice

Laboratory Errors in Medical PracticeMohammad Tanvir IslamAssistant Professor , MedicineBangabandhu Sheikh Mujib Medical University

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

“Smart people learn from their mistakes.

But the real sharp ones learn from the mistakes of others.” 

 Brandon Mull

Why did the TITANIC sink?

Laboratory Testing CyclePre-Analytic

phaseOrdering a test

Order transferred to lab

Identifying information entered

Specimen obtained

Analytic phase

Specimen analyzed

Post analytic phaseReport generated

Result conveyed to clinician

Data interpretedClinical response to

result

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

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

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

Clinical Performance Characteristics

• Prevalence• Sensitivity• Specificity• Efficiency• Positive Predictive Value• Negative Predictive Value

• 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

Shotgun versus Rifle

Common Causes of Pre-analytical Error

Biological• Age• Sex • Race (Blacks vs. Caucasians)

Timing of test Behavioral• Diet• Obesity• Smoking• Alcohol intake• Caffeine intake• Exercise• Stress

Diseases: • Hypothyroidism • Nephrotic syndrome/chronic renal

failure • Biliary tract obstruction

Drug Therapy: • Amiodaron – on thyroid profile• Diuretics –on pleural fluid• Propanolol • Oral contraceptives• Prednisolone-on immune markers

Timing of test

• Hepatitis virus • Dengue serology• Cardiac enzymes• Pencreatic enzymes• Widal test

• 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)

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

Analytic

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

Post-Analytic

• Failure in reporting 18.5%-47%• Erroneous validation of analytical data• Improper data entry

•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

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

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

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.

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.  

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

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