Unless you have other health conditions such as heart conditions a home sleep study should be quite sufficient to do a diagnosis. You should first ask for a copy of the sleep study report. It should have been prepared and reviewed by a sleep specialist doctor. It should give you an overall AHI number, as well as a breakdown of the central apnea events, obstructive events, and hypopnea events. Based on the AHI there is a rating system of the severity of the apnea.
None/Minimal: AHI < 5 per hour
Mild: AHI ≥ 5, but < 15 per hour
Moderate: AHI ≥ 15, but < 30 per hour
Severe: AHI ≥ 30 per hour
There should also be an oxygen desaturation measurement. 95% or higher is normal. 90% is good. Less than that starts to be a concern. It sounds like oxygen desaturation is not a problem for you, which in turn suggest your apnea is not likely severe. However, there should be an AHI number to determine where you stand with apnea.
If you are in the Mild category you could use a CPAP or try a dental device. The dental devices are typically more expensive than a CPAP though. If you are in the Moderate or Severe category you should use a CPAP.
I was diagnosed with an AHI of 33 based on a home sleep study only. My general practice doctor used it to prescribe a CPAP and I bought a complete package including a mask on line for about $900 Canadian. If you go that route I would suggest the ResMed AirSense 10 AutoSet for Her. It automatically adjusts the pressure and there really is no need for an overnight titration test to determine your optimum pressure. The machine will find the pressure you need. The For Her version of the machine includes an extra program that may be helpful to a female or male.
So, unless there are some other complicating medical conditions it would seem to me that if you do have apnea (and you need the AHI number to confirm that) you would be better off spending your money on an auto CPAP machine. Assuming you are in the US you will need a prescription to get one though, unless you can find a used machine. Here is one I found on line in the US. The price seems high to me, so you should look around and see if you can get a better price. If you are in Canada I can give you a link with better prices, but I don't think they will ship to the US.
ResMed AirSense™ 10 AutoSet™ For Her
But your next step should be to call your doctor and ask for more information such as a written copy of the sleep report. You need the AHI number and you need to know if the primary component is obstructive apnea and hypopnea. They can be reduced with a CPAP. If it is central apnea then it is more complex and you may need more than the basic auto CPAP. If it is just basic apnea then ask him why you would need another study, and if he will just write a prescription for an auto CPAP now. To me it doesn't seem to make a lot of sense to do a $5000 study to determine if you need a machine that will cost under $1000.
Hope that helps some. Just post again with any questions.
Degree of oxygen desaturation is not necessarily an accurate measure of the severity of OSA, it is only one piece of the puzzle. It is very possible (I have seen it many times) for a person to have a very high AHI but their events only to cause small oxygen desaturations. Their oxygen saturation may never dip below 90%. However, it is the arousal process at the end of each event which causes most of the damage to your organs, more so than the drop in oxygen (although this is also not good). This is one of the main reasons why AHI is the standard measure of severity of OSA rather than a function of oxygen saturation. Both AHI and oxygen levels are part of the picture, but there are many things which can can contribute to the impact which OSA has on someone physically and mentally. Obviously it takes a bit of thought and effort to take all of this into account, which is why a good doctor is so valuable and why doctors who just want to churn patients through for the money can be so destructive.
The cost of that sleep study seems high to me. I'm in the US, on Medicare, and have seen the costs for my 4 sleep studies (don't ask). The sleep studies were around $ 1000, with Medicare negotiating that down to around $ 500. The doctor that read the results and wrote the report, charged around $500. Then of course I had to go back to the sleep doctor for my prescription, that was another $400. Luckily for me, everything, including a resmed10, was paid for by Medicare
One more question to ask your doctor is if the overnight study is actually a titration study. They are done to determine the set pressure of a fixed pressure CPAP. If you buy a fixed pressure CPAP it may only be about $80 cheaper than an auto version. A titration study to determine pressure is not necessary with an autoset machine. Doesn't make much sense to spend $5000 to save $80!