Not every diagnostic test involves drawing blood or taking a picture.

Sometimes your healthcare provider wants to know how something in your body is working.

How is your heart beating?

How well are your lungs moving air?

What happens to your breathing while you sleep?

How strong are your bones?

These questions require different kinds of tests.

You may hear names like ECG, echocardiogram, pulmonary function test, sleep study, or bone density scan.

They can sound complicated.

But each is simply another tool designed to answer a particular question.

ECG or EKG: Looking at Your Heart’s Electrical Activity

Let’s start with something confusing before the test even begins.

An ECG and an EKG are the same test.

Both names refer to an electrocardiogram.

Your heart has an electrical system that helps control how it beats. An ECG records that electrical activity.

Small adhesive patches called electrodes are placed on your chest and sometimes your arms and legs. Wires connect the electrodes to the ECG machine.

The test is generally quick and painless.

And no—the machine isn’t sending electricity into your heart.

It is recording the electrical activity your heart is already producing.

An ECG can provide information about your heart rate and rhythm and may offer other clues about what is happening with your heart.

An Echocardiogram Is Something Completely Different

The names sound similar.

ECG.

Echocardiogram.

But they aren’t the same test.

An echocardiogram, often simply called an “echo,” uses ultrasound technology to create images of the heart.

Instead of primarily recording electrical activity, an echocardiogram allows healthcare professionals to see the heart’s structure and movement.

It can provide information about things such as the heart’s chambers, valves, pumping function, and blood flow.

For a standard echocardiogram, gel is placed on your chest and a handheld device called a transducer is moved across different areas to obtain images.

If you have already had an ECG and your doctor then orders an echocardiogram, it doesn’t necessarily mean something suddenly became worse.

The two tests answer different questions.

One looks primarily at electrical activity.

The other gives information about structure and function.

Pulmonary Function Tests: How Well Are Your Lungs Working?

Sometimes looking at a chest X-ray or CT scan isn’t enough.

Your healthcare provider may want to know how well your lungs actually function.

Pulmonary function tests—sometimes called PFTs—are a group of breathing tests.

One common test is spirometry.

You breathe into a mouthpiece connected to a machine. You may be asked to take a deep breath and then blow out as hard and as completely as you can.

It sounds simple.

But if you’ve never done it before, you may wonder whether you’re doing it correctly.

Don’t worry.

The person performing the test will coach you.

You may be asked to repeat the maneuver several times because consistent effort helps produce useful measurements.

Depending on why the testing is being performed, you may have additional breathing measurements as well.

Why Would I Need Breathing Tests if I Already Had Imaging?

Because a picture and a measurement of function aren’t the same thing.

Imaging can show healthcare professionals what parts of your lungs and chest look like.

Pulmonary function testing can provide information about how your respiratory system is working.

Sometimes doctors need one.

Sometimes they need the other.

Sometimes they need both.

This is another example of why diagnosis rarely comes from one magic test.

Sleep Studies: What Happens After You Fall Asleep?

You may be perfectly capable of describing how you feel during the day.

But what happens while you’re sleeping?

That is much harder to report.

A sleep study collects information while you sleep.

Depending on the type of study, sensors may monitor things such as your breathing, oxygen level, heart activity, movement, and sleep patterns.

Some studies take place overnight in a sleep center.

Certain types of sleep testing can be performed at home when appropriate.

If you are having an overnight laboratory study, the idea of sleeping while attached to monitoring equipment may sound impossible.

That’s a common concern.

You aren’t expected to have the most relaxing night of your life.

The goal is to collect enough useful information about what happens while you sleep.

“But I Barely Slept!”

Patients sometimes leave a sleep study convinced the test couldn’t possibly have worked because they slept terribly.

Don’t assume that.

The sleep team can determine whether enough usable information was collected.

If there wasn’t, they will tell you what happens next.

You don’t need to judge the quality of the study yourself.

Bone Density Scans: Looking at Bone Strength

Bones look solid, but they are living tissue that changes throughout our lives.

A bone density test—often called a DEXA or DXA scan—uses low-dose X-rays to measure bone mineral density.

It is commonly used to help evaluate bone health and the risk of fractures.

During the examination, you generally lie on a padded table while the scanner measures specific areas of your body, commonly including the hip and spine.

The test is usually quick and noninvasive.

You won’t feel the X-rays.

What Do Bone Density Numbers Mean?

After a DXA scan, you may see terms such as T-score or Z-score in your report.

And, naturally, the internet makes it possible to immediately start searching those numbers.

Resist the urge to diagnose yourself from a score alone.

Your healthcare professional considers the result along with other information that may affect your overall fracture risk.

The most useful question isn’t:

“Is my number bad?”

It is:

“What does this result mean for my bone health, and do I need to do anything differently?”

Why Am I Having This Test?

This may be the most useful question throughout the entire Diagnostics series.

Not:

“What diseases can this test find?”

But:

“Why is my healthcare provider ordering this test for me?”

Maybe your doctor wants to understand your heart rhythm.

Maybe they want to see how effectively your heart is pumping.

Maybe they’re measuring your breathing.

Maybe they’re trying to understand what happens while you sleep.

Maybe they’re assessing your bone strength.

Knowing the question often makes the test itself much easier to understand.

Ask How to Prepare

Some specialized tests require little or no preparation.

Others may have specific instructions.

You may be asked about medications.

You may be told what to wear.

You may receive instructions about eating, drinking, caffeine, smoking, exercise, inhalers, skin products, or other things depending on the test.

Follow the instructions you receive for your examination.

And if you aren’t sure, ask before the day of the test.

A simple phone call can prevent arriving only to discover that the test needs to be postponed.

Understand What Happens Afterward

Before you leave, ask:

“When should I expect the results?”

“Who will explain them to me?”

“Will they appear in my patient portal first?”

“Does this test give us an answer, or is it one part of the evaluation?”

That last question can be particularly helpful.

Sometimes the result provides exactly the information your healthcare team needs.

Sometimes it leads to another test.

Sometimes it helps rule something out.

Sometimes it needs to be interpreted alongside everything else.

Different Questions Need Different Tools

Modern medicine can listen to the electrical signals of your heart.

It can watch your heart move.

It can measure the air traveling through your lungs.

It can collect information about your body while you sleep.

It can estimate the density of your bones without ever making an incision.

That’s remarkable.

But none of these tests exists to tell the entire story of your health.

Each answers a particular kind of question.

So when another unfamiliar test appears on your schedule, you don’t need to memorize how the machine works.

You don’t need to learn how to interpret the numbers.

And you don’t need to become your own cardiologist, pulmonologist, sleep specialist, or bone expert.

You need enough information to understand what is happening to you.

Ask:

“What are we trying to learn?”

Because once you understand the question, the test often becomes a lot less mysterious.

References

National Heart, Lung, and Blood Institute (NHLBI). Electrocardiogram.

National Heart, Lung, and Blood Institute (NHLBI). Echocardiography.

National Heart, Lung, and Blood Institute (NHLBI). Pulmonary Function Tests and Sleep Studies.

National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS). Bone Mineral Density Tests: What the Numbers Mean.