Ann Lab Med.  2013 Sep;33(5):319-325. 10.3343/alm.2013.33.5.319.

Evaluation of the Performance of a Micromethod for Measuring Urinary Iodine by Using Six Sigma Quality Metrics

• Hussain H
• Khalid NM
• Selamat R
• Wan Nazaimoon WM

• KMID: 1781336
• DOI: http://doi.org/10.3343/alm.2013.33.5.319

Abstract

BACKGROUND
The urinary iodine micromethod (UIMM) is a modification of the conventional method and its performance needs evaluation.
METHODS
UIMM performance was evaluated using the method validation and 2008 Iodine Deficiency Disorders survey data obtained from four urinary iodine (UI) laboratories. Method acceptability tests and Sigma quality metrics were determined using total allowable errors (TEas) set by two external quality assurance (EQA) providers.
RESULTS
UIMM obeyed various method acceptability test criteria with some discrepancies at low concentrations. Method validation data calculated against the UI Quality Program (TUIQP) TEas showed that the Sigma metrics were at 2.75, 1.80, and 3.80 for 51+/-15.50 microg/L, 108+/-32.40 microg/L, and 149+/-38.60 microg/L UI, respectively. External quality control (EQC) data showed that the performance of the laboratories was within Sigma metrics of 0.85-1.12, 1.57-4.36, and 1.46-4.98 at 46.91+/-7.05 microg/L, 135.14+/-13.53 microg/L, and 238.58+/-17.90 microg/L, respectively. No laboratory showed a calculated total error (TEcalc)CONCLUSIONS
UIMM showed unacceptable performance for the iodine deficiency levels and variable performance at other concentrations according to different TEas.

Keyword

Urinary iodine; Method evaluation; Sigma metrics; Quality control; Method acceptability

MeSH Terms

Humans
Iodine/*urine
Laboratories/standards
Quality Control
Spectrophotometry/*standards
Urinalysis/*standards
Iodine

Figure

• 

  Fig. 1 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). According to urinary iodine ranges in Table 1.Abbreviations: L, low control; M-L, medium-low control; M-H, medium-high control; H, high control.

• 

  Fig. 2 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. According to urinary iodine ranges in Table 1.Abbreviations: L, low control; M-H, medium-high control; H, high control.

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