2.1. Quality management system

The urinary iodine laboratories (there are five laboratories in the country) were formed under the National IDD Eradication Program parallel with the initiative by the World Health Organization (WHO) for eliminating IDD worldwide. Quality management has been practiced throughout the Ministry of Health following the twelve elements outlined by WHO [8] (Figure 2). However, in this chapter, only the quality control aspects related to the urinary iodine laboratory quality management will be discussed, mainly on the processes related to the analysis.

Research from the year 2005 until 2006, comprised of sensitivity, precision, linearity, recovery

Understanding Quality Control with Urinary Iodine Estimation

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Training is important to enhance skills and competency in performing laboratory work. Maintenance of instruments is vital to ensure adequate heating during sample digestion, correct pipetting of samples and reagents, and accurate absorbance reading. Another important precaution to be made is to avoid contamination from salt iodine laboratory and unclean glassware. Since iodine is easily evaporated, iodine in salt which are usually present in parts per million (ppm) can be dispersed in the air in the same room environment and interfere with urinary iodine measurement which is in parts per billion (ppb). Inadequate cleaning of glassware may cause false detection of high concentration of iodine in urine. Reagents shelf-life should also be abided strictly as aged reagents may cause internal quality control (IQC) values to be out of limits.

IQC sample preparation follows the order of %CV ≤ 20% for Low control, ≤15% for Medium control and ≤10% for High control, in obtaining allowable ranges (mean 2SD) from replicates of samples of n ≥ 20. The order of %CV set for the laboratory superseded the % CV set by TUIQP, previous EQA program for urinary iodine which set %CV of 20% for all Low, Medium and High control ranges. Each control level (Low, Medium or High) should be included in the assay with minimum replicate of n = 2. External Quality Assurance (EQA) was done once or twice/year (2006–2009) and is currently being done for three cycles/year (2010-present). Current EQA program provides four concentration levels of samples and requires to be assayed in

Evaluation is performed from IQC and EQA results. IQC results are obtained from every assay while EQA results are obtained from every cycle of the program. Laboratory performance was also determined by conducting evaluation using the Six Sigma quality metrics which focused on the laboratory achievement as compared to the world-class level of Sigma-6 [10]. Evaluation

Corrective actions are made upon every occurrence of non-conformance. Corrective actions are meant to troubleshoot problems and prevent them from being repeated. Relevant IQC rules [11] are to be obeyed and corrective actions are done accordingly to improve quality of test. Improvement may lead to better laboratory practices and the cycle of the Quality System

A well-managed laboratory quality system will enable good laboratory practice, assessment of method, instruments and laboratory performance, and will help the interpretation of respondent results by knowing the accuracy of the method used for Urinary Iodine measurement.

and method comparison [9].

2.2.2. Laboratory practices

2.2.3. Control

2.2.4. Evaluation

2.2.5. Improvement

should be done periodically.

duplicates in three independent assays (n = 6).

(Figure 3) continues as it gets better throughout time.

Figure 2. The 12 elements of quality management outlined by WHO [8].

#### 2.2. Quality system in a urinary iodine laboratory

#### 2.2.1. Method

Following the Quality System (Figure 3), it started with method modification done in 2004 with migration from performing test wholly in test tubes to performing test half-way in test tubes (during sample digestion) and half-way in 96-well microtiter plates (during reagent mixing and absorbance reading). Method validation was done by the Institute for Medical

Figure 3. Flowchart of Quality System in the urinary iodine laboratory at the Institute for Medical Research (IMR), Malaysia.

Research from the year 2005 until 2006, comprised of sensitivity, precision, linearity, recovery and method comparison [9].

## 2.2.2. Laboratory practices

Training is important to enhance skills and competency in performing laboratory work. Maintenance of instruments is vital to ensure adequate heating during sample digestion, correct pipetting of samples and reagents, and accurate absorbance reading. Another important precaution to be made is to avoid contamination from salt iodine laboratory and unclean glassware. Since iodine is easily evaporated, iodine in salt which are usually present in parts per million (ppm) can be dispersed in the air in the same room environment and interfere with urinary iodine measurement which is in parts per billion (ppb). Inadequate cleaning of glassware may cause false detection of high concentration of iodine in urine. Reagents shelf-life should also be abided strictly as aged reagents may cause internal quality control (IQC) values to be out of limits.
