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BENEFIT OF :
SIGMA METRIC IN CLINICAL LABORATORY
48.000-96.000 patients deaths/year is caused by errors ( IOM-USA)
70% of all informations used for patient care is provided by the clinical laboratory.
The challenge is to ensure “error-free”processes …, from pre-analytical, analytical, and to the post-analytical, functions of laboratory services.” ....
Primum non nocere (Galen)
QUALITY CONTROL
Internal QC
External QC
Peer Group QC
Preanalytical QC ? ACCREDITATION
KARS, KALK, ISO 15189 AUTOMATION CONTINUOUS EDUCATION AND TRAINING
The old pippettes have been replaced by large, computerized , advanced instruments,
WHY would you want to use a 50 years old QC rules on a cutting edge instruments?
INTERNAL QUALITY CONTROL
Offer methodology for measuring process performance quantitatively
If you can’t measure quality, you can’t manage it.” ( JO Westgard)
HIGH QUALITY TOP QUALITY
INTERNATIONAL QUALITY BEST QUALITY
WORLD CLASS QUALITY
1980 Introduced by Motorola 1990 Applied widely in manufacturing
industry 2000 Applied in service industry
Six Sigma : World Class Quality
6 SIGMA = WORLD CLASS
QUALITY
CURRENT SITUASION =3
SIGMA
PRA ANALYTIC
ANALYTIC
POST ANALYTIC
Lab A performance 3,5 – 4 S 1% error rate
If Patient B :-10 test :error probability 10%-2x/ week :error probability 20%
DEFECT = ERROR
IMPLEMENTATION OF SIGMA METRIC IN
CLINICAL LABORATORY
Check outcome count defects
Pre and post analytical phase
TAT < 60’ , If > 60 ‘ defects
Characterizing variation of process
Analytical phase
Quality requirement = bias + imprecisionx + quality requirement = x + (bias + 6SD)
if Bias is O (zero):
x + quality requirement = x + 6SD
6S or 6SDs of process variation should fit within quality requirement
If bias : 4mg/dL =2%CV =(Tea – Bias)/ 6
= (10-2)/6 = 1,3 %
SETTING PERFORMANCE SPECIFICATION MEASURING ANALYTICAL PROCESS
QUALITY SELECTING IQC PROCEDURE SELECTING INSTRUMENT AND METHOD
SETTING PERFORMANCE SPECIFICATION Quality Design and Control Process
Process for translating customer needs into product and production specifications
CUSTOMER NEEDS :
▪ QUICK RESULT
▪ GOOD SERVICE
▪ SAFETY
▪ CORRECT RESULT SIGMA
▪ ETC
*Preanalytical error
*Group and within subject BV
SETTING PERFORMANCE SPECIFICATION MEASURING ANALYTICAL PROCESS
QUALITY SELECTING IQC PROCEDURE SELECTING INSTRUMENT AND METHOD
Allowable Total Error (Analytical Outcome Criteria)
Clinical Decision Interval (Clinical Outcome Criteria)
Maximum allowable SD and Maximum allowable bias (analytical performance criteria)
TEa : decision interval,analytical performance, guidelines (CLIA,Biologivariation, RCPA, NCEP)
Bias : difference from true value (EQAS,Peer group, reference method)
S : CV / SD from precision study (IQC)
Sigma metric = ( TEa – Bias ) / S
RCPA CLIA AND PROFESIONAL GUIDELINE
- Choose lab quality requirement
- Document and review lab quality requirement
- Determine lab quality requirement
- Document and review lab quality requirement
.
ALP AST
• Traceability
• Measured
substance
• Method
BHCG
Daily laboratory QC :
Cover different staff, reagent lot, control and calibration
3-6 months
Based on lab mean and SD At clinical important level
Example : CHOLESTEROL
Quality requirement (Tea) 10% Bias 1% Imprecision 4.5%
Sigma = ( Tea – Bias ) / S = (10 – 1)/4.5 = 2 = (308.537 defects / million tests)
Y axis : allowable inaccuracy ( bias, %) TEa
Clinical desicion interval
X axis : allowable imprecision for certain sigma ( CV,%)
Sigma metric = ( TEa – Bias ) / S
- X axis : allowable imprecision for certain sigma ( CV,%)
Ex : Tea = 12%, Bias =0%2S : max CV = 12/2 = 6%3S : max CV = 12/3 = 4%4S : max CV = 12/4 = 3%5S : max CV= 12/5 = 2.4%6S : max CV = 12/6 = 2%
- Albumin : Tea 12%
- Bias : 3%- CV : 3 %- Sigma : 3S
SETTING PERFORMANCE SPECIFICATION MEASURING ANALYTICAL PROCESS
QUALITY SELECTING IQC PROCEDURE SELECTING INSTRUMENT AND METHOD
ANALYTICAL OUTCOME CRITERIA
(TEa)
BIAS and CV/SD
QC RULES AND CONTROL NUMBER
ACCURACY and PRECISION
CLINICAL OUTCOME CRITERIA
ELEMENTS IN ANALYTICAL QUALITY :
Imprecision
Inaccuracy
Instability of measurement procedure
QC rules
GOOD QC RULES High error detection Low false rejection Low cost
QCRULES Number of QC Level Number of Run QC Rules
TEa : decision interval,analytical performance, guidelines (CLIA,RCPA, NCEP)
Bias : difference from true value (EQAS,Peer group, reference method)
S : CV / SD from precision study (IQC)
Sigma metric = ( TEa – Bias ) / S
POTASSIUM : Quality requirement (TEa) :10% (CLIA) Lab X ,instrument Y : CV1.5%, Bias 1% Sigma metric : (TEA – Bias)/ S = (10-1)/1.5 = 6 QC Program : N=2 / 3,5 s control limit
CHOLESTEROL : Quality requirement (TEa) : 10% (CLIA) Lab A, instrument B : CV4.5%, Bias 1% Sigma : ( TEa – Bias ) / S = (10 – 1)/4.5 = 2 QC Program : Maximum N , Multirules and Max
prevention action
SIGMA
6 5 4 3
QC NO AND QC RULES
N2/3,0-3,5 S N2/2,5-3,0 s N4/Multirules Max QC with
Max supervision ,Max experience
Different parameter Easy to difficult to handle
Different QC rules for different parameter With the help of Laboratory Information
System create individualize QC rules and monitoring each parameter
INVENTORY GROUPING TROUBLE SHOOTING AND IMPROVEMENT ; Instrument
Reagen
Methods
Procedures
Staff START WITH QC RULE WITH HIGH ERROR
DETECTION
SETTING PERFORMANCE SPECIFICATION MEASURING ANALYTICAL PROCESS
QUALITY SELECTING IQC PROCEDURE SELECTING INSTRUMENT AND METHOD
SETTING PERFORMANCE SPECIFICATION MEASURING ANALYTICAL PROCESS
QUALITY SELECTING IQC PROCEDURE SELECTING INSTRUMENT AND METHOD
SELECTING INSTRUMENT AND REAGENT
Customizing to customer and laboratory
requirement
Fewer errors, Fewer number of controls, less frequent
testing of controls, simpler control rules Better analytic quality
Analysis by Sten Westgard of 2007 AACC Poster: Gough SA, et al. Site Evaluation of Abbott Architect c16000. Clin Chem Chem 2007;53(s):A228.
SIX SIGMA IN CLINICAL LABORATORY:
Determining laboratory goal Selecting instrument and method Process quality monitoring Internal Quality Control Plan Patient satisfaction and safety
THANK YOU
James O. Westgard. Six Sigma Quality Design and Control .2nd ed,Westgard QC,Inc.2006
Six Sigma .A Quality Metric for Clinical Laboratory. Abbott Workshop Series