You'll need a copy of your most-up-to-date DOT MIS form handy.
Is an employee missing a pre-employment drug test?
Have you hired new employees? You may have forgotten to notify them to take a pre-employment drug test. If so, make sure that every new covered employee has a pre-employment drug test. In section 3 Drug Testing Data, look at the total pre-employment tests in column 1. The total pre-employment drug tests should equal the number of new hires.

If you opt-in for pre-employment alcohol testing, this should also be equal. Check the pre-employment total in Section 4 Alcohol Testing Data. A discrepancy could mean a missing record or a test that was never ordered.
Is your random testing pool meeting the minimum testing rates?
Your random testing rates should be at least equal to the minimum testing rates posted by the DOT. Of course, this is for the whole year (Jan. 1 - Dec. 31). In section 3 column 1, take your total number of random tests and divide this by the total number of employees in each category.
If you're checking the rates mid-year, make sure you're on track. For example, if your random drug testing rate is 50%, you should have close to 25% completed by June.
Are you aware of all your positive drug tests?
Eyeball your positive totals in section 3, columns 3, 9, 10, 11, and 12. You should be aware of any positive drug test results and refusals for your program. If not, there's a big problem. Speak with your account rep or administrator if something seems out of place.
The same goes for section 4 Alcohol Testing Data. Look at the positive totals in columns 6, 7, and 8.
There are other reasons for testing such as post-accident and reasonable suspicion but, these are case by case. The Designated Employer Representative (DER) is the best person to audit your program using the DOT MIS form. They receive every test result so, they can tell if the totals seem out of place. If the DOT has selected your company to submit it's MIS data collection form, don't forget, it's due by March 15.