Principles of Internal Quality and

External Quality AssuranceDr Kapil Yadav, Prof MG Karmarkar,

International Council for Control of Iodine Deficiency Disorders (ICCIDD),

All India Institute of Medical Sciences (AIIMS), New Delhi

25th February, 2010

Quality Assurance (QA) and Quality control (QC)

• Two terms used interchangeably though their meanings differ.

• Quality assurance is a proactive and continuous process of monitoring a system for reproducibility and reliability by:1. Setting standards of performance & designating

responsibility2. Ensuring definitive corrective actions are taken when the

criteria not met3. Performing measurements within a stated level of

confidence

Quality Control (QC)

• A quality control system is an indicator system for documented performance and actions that: 1. Provides a record of consistency of performance2. Records action taken when performance fails to

meet standard

• Thus quality control is tool by which the principle of quality assurance is achieved.

Elements of QA system

• An inventory agency responsible for coordinating QA/QC activities;

• A QA/QC plan;• General QC procedures;• Functions of participants• Reporting, documentation, and archiving

procedures.

Internal Quality Assurance

• Steps taken by the implementing laboratory to ensure that the process/system used by them to estimate salt iodine content are consistent and operate with a specified level of confidence.

External Quality Assurance

• Steps taken by an external review agency to ensure that the process/system used by the implementing laboratory to estimate salt iodine content are consistent and operate with a specified level of confidence.

Steps in Internal Quality Assurance: 1

• Step1: Preparation of known value samples

• Step 2: Analysis of known value sample with every batch of salt to be tested.

• Step 3: Plotting Levy Jenning (L J) plot.

Levy Jenning Plot

20

10

0

30

40

50P

P

M

of I2

Levy Jenning Plot

Mean

+ SD

- SD

Day of Month

Levy Jenning Plot

Known value salt preparation

Test No. Value Day of MonthValueValue- Mean/SD

1 34 16 32 -0.540312 34 17 33 -0.124693 36 18 34 0.2909384 31 19 35 0.7065645 32 20 31 -0.955946 35 21 32 -0.540317 36 22 31 -0.955948 29 23 33 -0.124699 31 24 34 0.290938

10 35 25 33 -0.1246933.3 26 32 -0.540312.41 27 33 -0.12469

28 32 -0.5403129 32 -0.5403130 29 -1.7871931 34 0.290938

1 32 -0.540312 31 -0.955943 29 -1.78719

Name of Laboratory Reporting Month

Known value MeanKnown value SD

-4

-3

-2

-1

0

1

2

3

4

1 4 7 10 13 16 19 22 25 28 31

Value- Mean/SD

Steps in Internal Quality Assurance: 2

• Step 4: Monitoring and feedback based on results of L J plot.

• Step5: Fixed number of samples to be collected randomly on different days and analyzed in duplicate.

Steps in Internal Quality Assurance: 3

• Step6: Salt samples along with the results to be sent to the reference laboratory each month (at least 50gms for each sample).

• Step7: The reference laboratory will analyze these salt samples in duplicate and then compare the results with the values obtained by laboratory which sent the samples.

Steps in External Quality Assurance: 1

• Step 1: The reference laboratory will analyze six salt samples (different brands) purchased from the market, six times each.

• Step 2: Find the Mean and the Standard Deviation for each salt sample.

• Step 3: Reference laboratory will send 50 gms of each salt sample to the participating laboratory each month.

Steps in External Quality Assurance: 2

• Step 4: Participating laboratory will analyze these salt samples in duplicate and send the results to reference laboratory.

• Step 5: Reference laboratory then will compile the results, compare the values, and advise any remedial measures.

Thank You

“Quality assurance is not a fault finding mission but a method to ensure quality of results from each laboratory.”