What Can a Memory Screen Actually Settle?

A screening test is designed to catch things, not to confirm them. That sounds like a technicality. It is actually the single most useful thing to understand before you take one, because it explains why a worrying result so often turns out to be nothing.

What Do the Numbers on a Screening Test Mean?

Two numbers get quoted. Sensitivity is how often the test catches people who do have the condition. Specificity is how often it correctly clears people who do not.

Both can look excellent and the test can still produce mostly false alarms. That is the part nobody explains, and it is not a defect in the test.

Why Do Good Numbers Still Produce False Alarms?

Because it depends how common the condition is.

Take a two-question depression screener used in general practice, one of the best studied short screens there is. At a middling cut-off it catches about 83% of people with major depression and correctly clears about 90% of those without it. Genuinely good numbers.

Now put it in a population where about 7 in 100 people have major depression. Of everyone the test flags, only about 38% actually have it. Nearly two thirds of the positive results are false alarms, from a test performing exactly as designed.

The reason is simply that there are far more people without the condition than with it, so even a small percentage of them wrongly flagged outnumbers the true cases.

So What Is a Screen Good For?

Deciding who should be looked at more closely. That is all, and it is genuinely valuable, because the alternative is that nobody gets looked at until the problem is obvious.

What a screen cannot do is tell you what you have. A result that says "worth a closer look" is doing its job. A result read as a diagnosis is being misused.

How Should You Read Your Own Result?

As information to take somewhere, not a verdict to sit with. If a memory screen flags something, the useful next step is a conversation with a doctor who can look at the rest of the picture: your medications, your sleep, your hearing, your mood and your history.

And if it flags nothing while you remain worried, that is also worth saying out loud to someone. A screen clearing you is not the same as nothing being wrong.

What a score means, or how the different kinds of test compare.

Where This Information Comes From

Kroenke K, Spitzer RL, Williams JB. The Patient Health Questionnaire-2: validity of a two-item depression screener. Medical Care 2003;41(11):1284-1292. doi:10.1097/01.MLR.0000093487.78664.3C