Graphical abstract Saudi poison control centers received 20,513 poisoning consultations calls in the year 2020.

Recently, urine substance of abuse (SOA) testing in the pre-employment/workplace and suspected SOA settings has become common in many countries all over the world. There have been multiple published research recommending the performance of the urine sample validity test (SVT) for substance of abuse testing administered in the pre-employment/workplace and suspected SOA settings. On the opposite side, very little researches focusing on variable procedures of urine adulteration in (SOA) testing process, including diluted, substituted, adulterated, and invalid tests. The current research investigated 7985 submitted urine drug test samples for sample validity test from pre-employment/workplace and suspected SOA settings in Saudi Arabia over one year. All preliminary immunoassay screen-positive urine sample drug tests were confirmed by gas chromatography/mass spectrometry and liquid chromatography/mass spectrophotometry. This article found that the prevalence of tampering (diluted, substituted, or invalid tests) in urine samples from the pre-employment/workplace and suspected settings were 0.87% and 0.69%, respectively. The percentage of diluted, substituted, adulterated and invalid urine specimens from the pre-employment/workplace and suspected cases were 75%, 21.4%, 1.7%, 1.7% and 63.6%, 36.4%, 0%, 0% respectively. The most common substance of abuse detected from the pre-employment/workplace and suspected specimens were cannabis, followed by amphetamines. We recommend that all urine samples taken for substance of abuse testing from both the pre-employment/workplace and suspected settings need to be investigated for validity.