Quality Evaluation of Urine Methamphetamine Color Test and Immunoassay Test - การประเมินประสิทธิภาพชุดทดสอบเมทแอมเฟตามีนในปัสสาวะโดยวิธีทางเคมีและวิธีทางภูมิคุ้มกันวิทยา

Abstract

Nowadays, Yaba or methamphetamine drug abuse becomes critical social problem in Thailand,
particularly among school children, collage students and blue - collar workers. Methamphetamine
urine test kit was an important equipment for screening test to detect Yaba in drug urine users.
The research was descriptive cross sectional study conducted from October 2010 to September
2011. The objective of this study was to evaluate the sensitivity, specificity, accuracy and false
positive results by using color test and immunoassay test with four different test kits in Nakhon
Nayok Hospital. Three were screening test products of Thailand and one was imported. Screening
tests were confirmed by thin layer chromatography. A total of 900 urine samples were sent for drug
trial. It was found that the sensitivity, specificity and accuracy of urine color test were lower than
those of immunoassay tests. False positive rate of urine color test were higher than that of immunoassay
tests, significantly (p < 0.001). All immunoassay test kits in this study were reported with
high sensitivity, specificity and accuracy. The imported product had the highest sensitivity (99.49
%), specificity (95.19 %) and accuracy (98.00 %) but it yielded the lowest false positive rate (4.81%).
Accuracy of an immunoassay based on methamphetamine test kits were higher than that of the color
test kits because the principle of immunoassay test was biochemical reaction while the color test
was only chemical reaction thus the immunoassay test showed higher specificity to drug abuse than
the color test. On top of this, color test had limited detection capability of method (cut off value
3,000 ng/ml) which is higher than immunoassay test (cut off value 1,000 ng/ml). These limits had
direct impacts as the color test also had lower sensitivity than the immunoassay test.
In selection of methamphetamine test kit for operation, quality assurance of the test compared
to the standard method is highly recommended particularly in case of apprehension, legal prosecution
and compulsory drug abuse rehabilitation that follow. With high accuracy of methamphetamine
test kit laboratory reports become more reliable and unbiased As such, all screening units for drug
abuse should use comparable high quality test kits.
Key words: methamphetamine test kit, color test, immunoassay test, methamphetamine, urine samples