We know that ADHD with adults is much more prevalent than was thought in the past. Actually, some 60% of children will suffer from this disorder also when they're adults (likely with changes in the disorder's symptoms). Additionally, we know today that most people who suffer from this disorder will suffer from another accompanying psychiatric disorder, likely depression.
On the other hand, depression is significant enough of a factor to cause a decrease in attention and focus as part of the symptoms of the illness itself.
Our recommendation is to continue the evaluation process your husband began, not to give up, but it's advisable to consult with a psychiatrist who specializes in ADHD in adults.
Occasionally, it's a good idea to consider effective treatment of depression and then to conduct the evaluation for ADHD.
Much success, and it's important to know that treatment is possible and in the end you'll find the way.