Laboratory errors.pdf

medical labs errors

2. Three phases of laboratory testing:
Pre-analytical:
Specimen collection, transport &
processing
Analytical:
Testing
Post-analytical:
Results transmission, interpretation, follow-
up, retesting

3. Preanalyticalvariables can dramatically
affect the results of laboratory tests.
Paying close attention to control the
preanalyticalvariables will help to
ensure accurate test resultsin clinical
laboratory.

4. No result is better than bad result.
Accurate result is the best of all.

5. Preparation prior to sampling
Sampling/Handling
Transport/Storage
Preparation prior to analysis

6. Pre-& post-analytical errors: > 90% of
errors
These potential errors are not inevitable
but could be prevented with an
accurate application of quality control,
continuing education and effective
collection systems.

7. Patient Identification
Sampling Technique
Collection Procedures
Specimen Transport
Specimen Processing

8. Attention to the preanalyticalvariables
associated with blood collection is
criticalin ensuring accurate test results.
Record significant variables on request
form.

9. Some patient variables that affect test results
Age
Genetic variation/ Race
Sex
Nutritional status
Diet
Exercise
Pregnancy
Timing
Special habits
Hemolysis, lipemia, Jaundice

10. When identifying the patient, get:
Full name
Age & sex
Address/Nationality
Identification number:
Hospital No for inpatients,
Identification band should contain the
above information (confirm before
venipuncture)

11. The highest frequency of errors occurs with
the use of handwritten labels & request
forms.
These can be eliminated by:
Confirming patient’s identifiers (name,
medical record number, date of birth,
room location or address)
Barcode technology.

12. Locate Patient
Label
Prepare Patient
Draw Sample
Dispose of supplies

13. TimingofCollection:
TherapeuticDrugMonitoring
-Peakandtroughcollectiontimes
BasalStateCollections
-Fastingrequirements:nofoodorliquid
exceptwater(10-12h),(12-14hforTG)
-2hpostprandial,fromthestartoffood.
Specimensaffectedbytimeofday,for
example,cortisol,ironandTSH.

14. Venipuncturerequiresexpertknowledge
andcriticaljudgment.
Phlebotomyerrorsmaycauseharmto
patientsorresultinneedlestickinjuryto
thephlebotomist.
Itcouldresultinmanypreanalytical
errorsinLabresults

15. PhlebotomyEducation
-Academic courseandtrainingunderthe
supervisionofaseniorphlebotomist.
ContinuousMedicalEducation
-Competency assessments (writtenand
observational).
-ProfessionalLicense.
PhlebotomyStaffing
-Adequate staffingtomaintaincollection
standards.
Technology
-Useofbarcode scannersforpatient
identification.

16. 1. Posture:
-Comfortably seated patient or supine for
20 min before sampling (not standing).
-The arm should be extended in a straight
line from the shoulder to the wrist.
2. Collection site:
-The median cubitalvein is the preferred
site.
-Veins on the hand or at ankle may be
used.

17. Cleaningofvenipuncturesite
-Thoroughcleaningwithalcohol
-Allowalcoholtodrycompletelytoavoid
stingingsensationandhemolysisofsample
-Iodineforbloodculturesamples(sterile
sample)
N.B:contaminationoccursin50%atsome
hospitalswithincreasedcosts&patient
overtreatment.

18. Avoid the arm with:
-Extensive scarring, hematoma, infection,
edema or burn
-On the same side of mastectomy.
-I.V. infusion (Document if IV ).

19. 3. Correct collection system :
-Vacutainersforlargeveinsinantecubitalfossa.
-Syringeforsmall,fragileveinsorveinsoutside
antecubitalfossa.
4.Venousaccess:
-Needleentryshouldbeat15-30odependingon
depthofvein.
-Needleentryshouldbeinsamedirectionasvein,
centeredovervein.
-Anchorveintopreventmovementduringneedle
entryandtoreducepaintopatient.

21. Tourniquet Application
-Tourniquet tied too close to venipuncture
site can cause hematoma.
Veins may not become prominent if
tourniquet is tied too high (> 3-4 inches
above venipuncturesite)
Tourniquet left for > 1 min can result in
hemoconcentration, affecting some test
results.
Tourniquet should be released as soon as
needle is in the lumen of vein and blood
flow is established.

22. Additives used:
EDTA,
Citrate,
Lithium heparin,
Fluoride/ Oxalate

23. Typical errors :
Incorrect tube
• cannot be analysed
• risk of contamination
Solution: New sample needs to be sent to lab.

24. Causes of Hemolysis
Traumatic venipuncture
Blood collected from area with hematoma
Vigorous shaking after collection
Milking the site when collecting capillary
samples
Blood collected using a small diameter needle.
High filling pressure through a narrow entrance
(e.gduring too vigorous sample aspiration)
Cooling down the sample < 0 °C.

25. Affectsanalytesthatarepresentat
higherconcentrationsinerythrocytes
thaninplasma(K,LD,AST,Mg,P)

26. Capillary Collections:
Appropriate site
-Heel stick: sides of bottom surface of the
heel (infants)
-Finger stick: third or fourth fingers,
perpendicular to fingerprint lines on
fleshy pads on finger surface.
Warmbefore collection to increase
capillary blood flow near skin surface.
Clean site with alcohol and allow to dry.
Discardfirst drop of blood.

27. 1.Blood Culture Bottles
2.Coagulation Tube
3.Serum Tube
4.Heparin Tube
5.EDTA
6.Glycolytic Inhibitor

28. Proper Tube Mixing:
Alltubeswithadditivesneedtobe
inverted(10times)tomixtheadditive
evenlywiththeblood.Impropermixing
ofthetubeaftervenipuncturecould
contributetosampleclotting.

29. ConsequencesTypical errors
hemolysis, hemoconcentrationTrauma, strangulation, stasis
dilution, false resultsIV contamination
incomplete lab results, repeat
sampling
Sample volume is insufficient
inappropriate anticoagulant:blood
ratio, false results
Incomplete filling of tubes
clotted, hemolysedsampleInappropriate mixing

30. Solution:
Lab report with preanalyticalcomment
(if problem recognized).
New sample is requested.

31. Blood should never be collected proximal
to the infusion site.
It is recommended that the laboratory be
informed of when and what type of infusion
were carried out and when blood samples
were taken.
If samples are to be taken from catheters,
the cannulashould be rinsed with isotonic
saline suitable for the volume of catheter.
The first 5 ml of blood should be discarded
before a blood sample is taken.

33. Propertransportofspecimensafter
collectionensuresqualityofsample&
tests.
Timing
-Somespecimensmustbetransported
immediately(ArterialBloodGases).
-Specimens forserumorplasma
chemistrytestingshouldbecentrifuged
andseparatedwithin2hs.

34. Temperature
-On ice: ABGs, Ammonia
-Warmed (37 C): cryoglobulins
-Avoid temperature extremes if
transported via vehicle.
Transport Container
-Some samples need to be protected
from light e.g. bilirubin.
-Transport in leak-proof plastic bags in
lockable rigid containers & avoid
agitation.

35. ConsequencesTypical errors
False results
(high K)
Delay in reporting
Burden and harm to
patient
Delay
sample stability deteriorates,
certain components break
down
Inappropriate storage
Solution: New sample is requested.

36. Registration, identification
Checking for clots
Centrifugation
Distribution
Storage (non routine daily analysis , for
post-analysis if it is needed)

37. ConsequencesTypical errors
Hemolysedsample, fibrin strand in
serum, clogging
Native blood centrifugatedbefore
clotting
False concentration or
precipitation, …… false result
Inappropriate melting of frozen
specimens
False results
Contamination
Inappropriate storage of samples in
lab (sample ID lost, contamination,
break down of unstable
components … etc.)
False resultsClots in anticoagulatedblood
Cryoglobulins

38. Clotted
Hemolyzed
Underfilled, overfilled
Insufficient quantity
Incorrect labeling
Unlabeled specimen
Incorrect patient
Incorrect specimen
Contaminated
Lost sample
Too old to process
Broken and leaking

40. The human role in sample collection
makes complete elimination of errors
associated with laboratory testing
unrealistic
However, good practices and
compliance with strategies for error
prevention can lead to a substantial
reductionin pre-analytical errors.