Lab Med Qual Assur.  2021 Jun;43(2):72-79. 10.15263/jlmqa.2021.43.2.72.

Development and Stability Evaluation of In- House Prepared External Quality Controls for Autoimmune Disease Tests

• Shin S
• Park J

• KMID: 2517261
• DOI: http://doi.org/10.15263/jlmqa.2021.43.2.72

Abstract

Background
The control samples for external quality assessment (EQA) must be highly stable during the EQA process. This study aimed to evaluate the stability of in-house prepared external quality controls for autoimmune disease tests, including anti-nuclear antibody (ANA), anti-double stranded DNA immunoglobulin G antibody (anti-dsDNA), anti-thyroglobulin antibody (anti-Tg), and anti-thyroperoxidase antibody (anti-TPO).
Methods
The in-house prepared external quality controls with two different levels (negative and positive for ANA and anti-dsDNA; low and high for anti-Tg; and anti-TPO) for each autoimmune disease test were prepared and stored at test temperatures of –20℃, 4℃, and room temperature (RT). The levels of each autoimmune disease test were measured at baseline and at 1 week, 2 weeks, 1 month, 3 months, and 6 months. The internal quality controls from the same batch run were also tested during the evaluation period.
Results
The negative and positive controls for ANA were stable for 6 months, regardless of storage temperature. The positive control for anti-dsDNA tended to increase in level at 6 months (P =0.033). The low and high anti-Tg controls tended to decrease in levels at 3 months (P =0.033 and P =0.042, respectively). The low control of anti-TPO decreased in level at RT compared to –20℃ at 1 week (P =0.026) and the high anti-TPO controls tended to decrease in level at 3 months regardless of storage temperature such as –20℃, 4℃, and RT (P =0.041).
Conclusions
The stability of in-house prepared external quality controls was influenced by different storage temperatures and durations. These results indicate that all EQA samples for autoimmune disease tests should be stored at –20℃ or 4℃ and be tested as soon as possible during the EQA process.

Keyword

Stability evaluation; In-house prepared quality controls; External quality assessment; Autoimmune disease tests