4. Participation in External Quality Assurance program

External Quality Assurance (EQA) is an ISO requirement, to confirm the quality of analysis. It shows the bias and precision of our assay and the position of our laboratory within the same test method group and against other test method groups. Participation in the EQA program increases confidence of laboratory personnel in performing the analysis.

and the former EQA program is the only existing program providing services to various urinary iodine laboratories worldwide. Since urinary iodine is easily evaporated and UIMM uses digested sample of only 30 μl out of 1250 μl of total volume, high %CV is usually high in the lower concentration range of the standard curve. EQUIP which set stricter %CV limit, leads

Understanding Quality Control with Urinary Iodine Estimation

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Figure 8. Urinary iodine micromethod's normalized method decision chart against The Urinary Iodine Quality Program (TUIQP) TEas based on the 2008 National IDD Survey EQA results (Lab A [n = 20], Lab B [n = 18], Lab C [n = 12], and Lab D [n = 6]) and the 2006 method validation study (MV). L indicates low control, M-L indicates medium-low control, M-H indicates medium-high control, and H indicates high control, according to urinary iodine ranges in Table 1 of reference [10] as reported in Hussain et al. [10] (image reproduced with permission of the rights holder, Annals of Laboratory

Figure 9. Urinary iodine micromethod's normalized method decision chart based on the 2008 National IDD Survey EQA results (Lab A [n = 20], Lab B [n = 18], Lab C [n = 12], and Lab D [n = 6]) and against EQUIP TEas. L indicates low control, M-H indicates medium-high control, and H indicates high control, according to urinary iodine ranges in Table 1 of reference [10] as reported in Hussain et al. [10] (image reproduced with permission of the rights holder, Annals of

Laboratory Medicine).

Medicine).

There are various methods which are under the External Quality Assurance Program, i.e. Sandell-Kolthoff method consists of three different assays: (1) done in tubes, digestion with chloric acid; (2) done in tubes, digestion with ammonium persulfate; (3) done in microtiter plate, digestion with ammonium persulfate. There are other methods such as using the autoanalyzer using dry ashing of urine in potassium carbonate. However, the method with highest sensitivity is the inductively-coupled plasma-mass-spectrometry (ICPMS) but small/ medium scale laboratories may not afford to purchase the instrument.

CDC's Ensuring the Quality of Urinary Iodine Procedures (EQUIP) program from the Centre for Disease Control and Prevention (CDC), Atlanta, U. S. A. is worldwide. To date, more than 84 iodine laboratories from more than 50 countries have participated. Our laboratory has participated since the year 2010 until present.

If any urinary iodine laboratories are interested to participate in the EQA program, please visit CDC's website. Application form should be completed and e-mail or fax it to CDC, and a confirmation e-mail will be received within 72 hours. The laboratory will then be enrolled immediately upon receipt of the form and will receive a set of EQA samples every February, June and October each year.

What each laboratory should do is to treat the EQA samples like normal respondent samples and run the EQA samples in duplicates in three assays on different days. Report of the results should be submitted before the deadline within 1 month after receipt of samples.
