Crespi Valeria, Maio Ramòna Consuèlo, Veronesi G, Gianfagna F, Taborelli S, Ferrario M M
Toxicology Laboratory, Occupational and Preventive Medicine, Varese Hospital, Varese, Italy.
Med Lav. 2015 Sep 9;106(5):374-85.
Previous reports revealed poor performance in identifying drugs of abuse users through first-level workplace drug testing (WDT), based on urine samples. In a cross-sectional study, we evaluated: (i) the effect of creatinine normalization of drug values from diluted urine samples (creatinine levels ≤ 20 mg/dL) on the prevalence of drug users; (ii) the independent procedure-related predictors of positivity and dilution.
Workers' urine samples were collected at the workplace or at our certified laboratory between 2008 and 2012. All samples were analysed for drugs of abuse by immuno-enzymatic method in our laboratory, according to the Italian WDT law. Detectable drugs of abuse concentrations lower than the positive cutoff values were normalized based on mean levels of urinary creatinine. Detectable concentrations of drugs were confirmed by GC/MS. Multivariate logistic regression was used to detect independent procedure-related predictors of positive and diluted urine samples.
Of the 3080 urine samples screened, 51 (1.7%) were found positive for some drugs of abuse (26 cannabinoids and 16 cocaine) and 116 (3.8%) were diluted. Seventeen out of 23 diluted urine samples with detectable concentrations of cannabinoids or cocaine were found positive after urine creatinine normalization and GC/MS confirmed both negative and positive results. This increased the percentage of positivity for cannabinoids and cocaine from 1.35% to 2.09% (+55%, p=0.0005), which is closer to the expected prevalence of drug users based on Italian self-reported surveys. Collection of samples in the laboratory was an independent predictor of positivity (OR=2.33, 95%CI 1.27-4.28) and diluted urine sample (OR=1.65, 95%CI 1.04-2.61).
Efficacy of first-level WDT could be improved by well-controlled pre-analytical procedures and urine creatinine normalization of detected concentrations of drugs of abuse.
先前的报告显示，基于尿液样本的一级工作场所药物检测（WDT）在识别药物滥用者方面表现不佳。在一项横断面研究中，我们评估了：（i）稀释尿液样本（肌酐水平≤20mg/dL）中药物值的肌酐标准化对药物使用者患病率的影响；（ii）与检测阳性和尿液稀释相关的独立程序预测因素。
2008年至2012年期间，在工作场所或我们的认证实验室收集工人的尿液样本。根据意大利WDT法律，我们实验室采用免疫酶法对所有样本进行药物滥用分析。低于阳性临界值的可检测到的药物滥用浓度根据尿肌酐平均水平进行标准化。药物的可检测浓度通过气相色谱/质谱法（GC/MS）确认。采用多变量逻辑回归来检测与检测阳性和稀释尿液样本相关的独立程序预测因素。
在筛查的3080份尿液样本中，51份（1.7%）被发现对某些药物滥用呈阳性（26份大麻素和16份可卡因），116份（3.8%）被稀释。在23份可检测到大麻素或可卡因浓度的稀释尿液样本中，有17份在尿肌酐标准化后被发现呈阳性，GC/MS确认了阴性和阳性结果。这使得大麻素和可卡因的阳性率从1.35%提高到2.09%（增加了55%，p = 0.0005），这更接近基于意大利自我报告调查的药物使用者预期患病率。在实验室收集样本是检测阳性（OR = 2.33，95%CI 1.27 - 4.28）和稀释尿液样本（OR = 1.65，95%CI 1.04 - 2.61）的独立预测因素。
通过严格控制分析前程序和对检测到的药物滥用浓度进行尿肌酐标准化，可以提高一级WDT的有效性。
