Far fewer people in Hawaii failed workplace drug tests in the third quarter of 2018, according to results from the largest company in the state doing such work.

Diagnostic Laboratory Services reported Thursday that positive tests for amphetamines, opiates, cocaine, marijuana and synthetic urine all plunged around 30 percent in the July-September period compared with the same quarter a year ago or the second quarter, or both.

Large swings up or down in drug test results are not uncommon, but Steven Brimmer, scientific director of toxicology at DLS, said it was surprising to see such a big decrease across all drug categories.

“It’s pretty unusual,” he said.

What the substantial decline in positive drug tests means is hard to say. It could be that fewer people are using drugs. Or perhaps fewer drug users are applying for jobs or being selected for drug tests at jobs they already have.

DLS does testing for the private sector as well as the state. Brimmer noted that a one-third drop in positive results represents relatively few people.

Typically, DLS does 7,000 to 10,000 tests in a quarter. Positive results in recent quarters have been close to 1 percent (70 to 100 people) for amphetamines and synthetic urine, around 3 percent for marijuana (210 to 300 people) and less than 0.5 percent for opiates and cocaine (less than 35 to 50 people).

In the third quarter, positive tests for amphetamines that include methamphetamines decreased to 0.63 percent from 1 percent a year earlier. That equates to a 37 percent decline representing 26 to 37 fewer people testing positive.

Brimmer said this drop was particularly nice to see. “Hopefully this means a decrease in meth use,” he said, adding that positive tests on the mainland for amphetamines were up significantly in the Midwest and South during the third quarter.

Positive tests for cocaine fell 30 percent to 0.26 percent in the third quarter from 0.37 percent a year earlier.

Marijuana detections dropped 29 percent to 2.7 percent from 3.8 percent in the same period.

The only test result that didn’t drop close to 30 percent year-over-year was opiates, which declined by 18 percent to 0.16 percent in the third quarter from 0.19 percent a year earlier. However, compared with the second quarter, positive tests were down 32 percent.

For synthetic urine, positive tests sank 39 percent in the third quarter to 0.87 percent from 1.25 percent a year ago. Brimmer said this could be because fewer people are using it to avoid testing positive for illegal drugs or that makers of the product have improved it to better avoid detection.