When a person has been advised a sleep test, many doubts start racing in their mind. The three significant uncertainties that arise in any person who has been asked to undergo a sleep study are -
- Difference between in-lab sleep test and home sleep test
- Which test would help in effectively diagnosing the disorder?
- Which test is better and affordable?
A major differentiating factor for sleep study test is the location of the sleep tests.
Home Sleep Tests: A Home Sleep Test or HST is a sleep test undertaken at the person’s home. For an HST, the person goes to a sleep clinic on the day of the test, pick-up his HST kit and gets apprised on how to perform the test, and the various do’s and don’ts. Once the test is completed by the user, he takes the kit back to the clinic where the data is uploaded after being reviewed by the concerned specialists.
In-Lab Sleep Study: As the name suggests, an in-lab sleep study is conducted in the sleep clinic. The patient has to reach the clinic for the test, complete the paperwork and is provided with an overview of the procedure. This overview is provided by an RPSGT (Registered Polysomnographic Technologist). The patient has to spend the night at the clinic for the test and once the test gets completed in the morning, can leave for his home.
When comfort and location are in question, the best bet for any patient is HST. This holds true especially for those patients who live in remote places, for whom making a clinic visit is very inconvenient and also costly. For these patients, the sleep clinics mail the HST kits to the person’s local physician who then guides the patient on how to undertake the test. Once the patient completes the test, the test kit is delivered back to the sleep clinic, and the results are sent to the sleep specialists.
Another key differentiator between the HST and in-lab sleep study is the primary purpose of the study. An in-lab sleep study is primarily an overnight sleep study. Also called a polysomnogram (PSG), the in-lab sleep study can test the patient for a wide range of sleep disorders such as breathing disorders, disorders relating to circadian rhythm, PLM (Periodic Limb Movement), insomnia, hypersomnia, among others. An HST, on the other hand, is capable of only testing the patient for breathing disorders like OSA (obstructive sleep apnea).
HST is generally used for diagnosing the patients with OSA. An HST will only be recommended if it is clear that the patient has high chances of having either a moderate or severe sleep apnea. The main reason for this is the tendency of HST's to underdiagnose the breathing disorders. If the patient has low-moderate or even a mild sleep apnea, the HST might conclude that the patient’s present sleep apnea condition is not severe enough to warrant a PAP machine or might even say the patient does not have symptoms of sleep apnea.
Patients who have co-morbid conditions associated with sleep disorders or are have medical conditions like COPD, heart and neuromuscular disorders are not recommended to undertake an HST.
Lot of monitoring devices are used when a person undertakes a PSG, which includes
Since an HST diagnoses just breathing disorders, it does not need a lot of monitoring devices. An HST kit would include devices which can be assembled by the patient on their own. These devices would consist of
- Electrodes for measuring brain activity
- Electrodes for measuring jaw muscle and eye activity
- Elastic belts for measuring the breathing effort
- Electrodes for recording muscle movement
- EKG monitors for measuring heart functions
- Other devices for measuring snoring, oxygen levels, and breathing activity
Regarding diagnosing sleep disorders accurately, a PSG is the most accurate study. Even for diagnosing OSA, a PSG would be the best bet. This is mainly due to the use of additional monitoring devices which would help the RPSGT to determine stage of sleep as well to know whether the patient is in a sound sleep.
- A small nasal cannula for measuring airflow
- A belt for measuring respiratory effort
- A finger clip for measuring oxygen level
In a PSG study, only when the patient is sound asleep would the data be recorded which makes the diagnosis more accurate. On the other hand, in HST, the study starts scoring from the beginning till the end, which often leads to improper or underdiagnosing of the sleep disorder. The HST tends to record the patient’s breathing even when he is awake (a phase where chances of sleep apnea are the lowest), which often leads to the wrong diagnosis.
When a person undertakes an in-lab sleep study, he is monitored closely by an RPSGT. The RPSGT can make necessary equipment calibrations according to the patient’s requirements as well as make necessary adjustments or changes to the equipment for getting the most accurate result. In an HST, there is no monitoring of the sleep test, and the user himself has to make necessary adjustments and calibrations to the equipment. One of the primary reasons for many HSTs’ failing to provide an accurate diagnosis is that if the patient does not wake up in the middle of the test to reattach any detached equipment, then the test might not have adequate data of results, causing the patient to retake the test.
When a patient goes for an in-lab sleep study, the test results are available very quickly, and the patient receives them relatively quickly. In a PSG, the RPSGT scores the study while the test is underway and provides these to the doctor for review the next working day. In HST, the results are delayed since the patient has to submit the machine to the clinic and the RPSGT scores it and forwards it to the sleep physician. The delay is often no more than two to three days.
Besides location and diagnostics, costs of the study act as a significant differentiator. HSTs’ are very cheap and costs nearly ¼ of the cost incurred during the in-lab sleep study. It is for this reason, a majority of the insurance companies make their clients undergo HST first. Proper screening by trained technicians during HST has resulted in many patients being accurately diagnosed as having moderate-to-severe sleep apnea, resulting in avoidance of expensive in-lab sleep studies.
Both PSG and HST have their pros and cons. Selecting the most appropriate test essentially boils down to the individual patient. For accurate diagnosis of sleep disorders with other co-morbid conditions, a PSG would be the best bet. On the other hand, if the sleep physician is reasonably convinced about the sleep apnea diagnosis in a patient and just wants to know the severity of the condition, then an HST would be the most suitable test.