Factors Affecting Laboratory Results

Flashcards covering pre-analytical, analytical, and post-analytical factors that influence laboratory test accuracy and quality indicators.

What are the three different phases that affect laboratory results?

The pre analytical, analytical, and post analytical phases.

What timeframe does the pre analytical phase encompass?

From the time the request is made to when the specimen gets to the laboratory.

What percentage of all errors in laboratory results can be accounted for by pre analytical errors?

As high as $70\%$ of all errors.

What are the two major causes of analytical errors?

Instrument error and User inadequacy.

What factors contribute to instrument malfunction in the laboratory?

The life span, type, and physical conditions of use and storage.

What operator-related issues can cause analytical errors?

Inability to follow laid down protocol, inability to follow the Standard Operating procedure, inability to obey rules, inability to read, tiredness, and poor lightening.

Who is responsible for troubleshooting intra laboratory sources of error?

The quality control officer.

What type of errors do post analytical errors mainly tend to be?

Transcription errors.

Which laboratory tests are given as examples that need to be requested in pairs?

Calcium and albumin, and ALP and GGT.

Why does a cortisol test specifically require timed patient preparation?

Because of the circadian rhythm.

How does starvation of more than $4\text{ weeks}$ affect biochemical parameters?

It reduces GGT, triglycerides, and urea, while uric acid and creatinine are increased.

Which parameters are affected by patient posture?

Protein and protein bound molecules.

What parameter is altered by patient stress?

Glucose.

What physiological effect can strenuous exercise have on laboratory results?

It can alter acid-base balance.

Which analyte is affected by the prolonged or improper use of a tourniquet?

Calcium.

Which analytes are affected by a haemolysed specimen?

Potassium, phosphate, and liver transaminases.

What practices can cause haemolysis of a specimen?

Improper specimen collection, forcing blood thru a needle, vigorous shaking of the specimen bottle, repeated freezing and thawing, and storage without centrifuging.

How does a lipemic specimen affect AST and ALT assays?

It affects AST and ALT assays read at $340\,\text{nm}$ (those assays that use NADPH).

What issues arise from an improper specimen quantity?

Specimen rejection or analysis of just part of the request, leading to specimens collected at different times for the same investigations and possible mis-interpretation.

What non-patient parameters can contribute to pre analytical errors?

Improper filling of forms, use of wrong specimen bottles, and tipping specimen from one bottle to the other.

What quality indicators were highlighted by a study conducted in Italy?

Appropriateness of test request in relation to the clinical question, legibility of request, ability to identify the requesting doctor and patient, properly and improperly filled forms, number of requests that are clotted, haemolysed, or in wrong bottles, and proper storage (avoiding dysfunctional fridges and freezers).