Tests and Diagnosis

Detailed questioning of the patient is the key to accurate diagnosis. Physical examination and appropriate investigations are also important.

Alternative causes of symptoms need to be considered and identified. 

Patients are often diagnosed by a cardiologist, neurologist, medicine for the elderly consultant or a paediatrician, although a GP can also diagnose PoTS. To be given a diagnosis of PoTS, a person needs to meet the definition and diagnostic criteria shown here.

Investigations 

Patients may undergo some or all of the tests below depending on their symptoms, medical history, examination and results of other tests.

Electrocardiography (ECG)

An ECG is performed to rule out any heart problems that may cause symptoms similar to those found in PoTS.

The Active Stand Test

The active stand test or NASA can be used to diagnose PoTS. Recently the Nasa Lean Test has also been adopted for use in diagnosing PoTS, but has not been studied in as much detail in PoTS. Under careful supervision, heart rate and blood pressure are measured after resting lying down, then immediately upon standing and then at frequent intervals until 10 minutes. This test should bring on symptoms of PoTS and some people may faint.

Head-Up Tilt Table Test

This involves lying on a table that can be tilted to an angle of 60 to 70 degrees in a quiet, dimly lit, temperature-controlled room. Blood pressure and heart rate are recorded in a continuous manner. After a period of 5 to 20 minutes of lying flat, the table is tilted head up. Although a diagnosis of PoTS should be made by an increase in heart rate of 30 bpm within the first 10 minutes, this upright position can last between 10 and 45 minutes. The patient will be asked how they are feeling during the test, so symptoms can be matched with heart rate and blood pressure.  The test will end if your blood pressure becomes too low, satisfactory results have been obtained, or the maximum time has elapsed.

If facilities are available, some patients are tilted after a carbohydrate drink (liquid meal challenge) or exercise.

24-hour heart rate monitor and ambulatory blood pressure

Heart rate monitor – Sticky patches are applied to the chest and are linked to a little box which is attached by a belt to your waist. It monitors heart rate over a 24-hour period.
Ambulatory blood pressure – A blood pressure cuff on your arm will intermittently check your blood pressure.
The patient is asked to go about their usual daily activities, trying to reproduce events that seem to cause the symptoms. A diary stating the time and activity performed at the moment when the symptoms started should be kept. Doctors look to see if there is a fast heart rate or drop in blood pressure at the time of symptoms.

Echocardiogram (Heart ultrasound)

This test is to check if the hearts structure is normal. In this test a technician will apply some jelly on the chest and will roll an ultrasound probe in many directions to create a 3-dimensional image of the heart. It is a painless and harmless test that is similar to the ultrasound scan used routinely during pregnancy to look at the unborn baby.

24-hour Urine Collection

Collection is made in a large bottle and tested for urinary sodium levels, as individuals with PoTS often have low levels of less than 170 millimole per 24 hours.

Another 24-hour urine collection may be carried out to test for high levels of noradrenaline and epinephrine to rule out pheochromocytoma (a growth on the adrenal gland) as a possible cause of symptoms.

Blood tests

Bloods are taken to rule out other conditions.  These may include:

• full blood count
• kidney function
• ferritin, vitamin B12, folic acid levels
• thyroid tests
• morning cortisol levels (to rule out poorly functioning adrenal glands)
• glucose
• vitamin D
• Coeliac screen (to check for Coeliac disease)
• Blood can also be taken for norepinephrine whilst lying and then standing (or when upright on the tilt table); if levels exceed 600 picogram/millilitre, it may suggest hyperadrenergic PoTS. However, most hospitals do not have facilities to analyse this test, so this test is not commonly offered. 

Other tests that may be carried out

Autonomic function screening tests. These tests require a special laboratory and are not available in most hospitals.

Thank you to Ruby Usiskin for producing the image. Subject to copyright by PoTS UK.