Metoprolol - does metroprolol affect drug test?

"Only 85 of the estimated 1,200 laboratories in the United States currently testing urine for drugs meet federal standards for accuracy, qualified lab personnel, and proper documentation and record-keeping procedures. Because private companies are not required to use certified drug testing labs, workers are being asked to put their job security in the hands of a drug test that has insufficient quality controls."

Even in labs that do meet the minimum standards, there is plenty of room for error. Your urine sample will change hands many times before its actual drug analysis, which increases the risk of mix-ups and errors. Also, the chemical reagents used in drug testing have a limited shelf life, which can cause "false positives". (A false positive is a sample showing a positive for drug metabolites when there are no metabolites in the person's system.)

Most states do not regulate the operations of urine drug test labs; in fact, some labs have fewer quality control regulations than restaurants. Your typical private employer may use any lab she/he chooses, which would most likely be the least expensive. Findings from the Center for Disease Control in Atlanta stated: "... the labs somehow detected cocaine in as many as 6 percent, and amphetamines in up to 37 percent of urine specimens that were 'blank" (those containing no drugs at all)."

False positive results during drug testing run high and no laboratory process is completely free from error. False positives also occur at high rates reported from 4 percent to over 50 percent. The high prevalence of false positives insures that people who are accused by the drug test are not necessarily drug users. False positives can occur for a number of reasons including: improper laboratory procedures, samples getting mixed up, paperwork being incorrect or lost, passive inhalation (second-hand smoke), and cross-reaction with prescription drugs and over-the-counter medications.

A USA TODAY report indicated that 15 percent of all urine drug tests yield a false positive due to cross-reacting substances. In a UCLA study of 161 legally prescribed and over-the-counter drugs, 65 gave false positive results. A National Institute of Drug Abuse study of 50 labs revealed that all 50 labs responded with some false positive results for drug tests.