What is the asserted date of initial delinquency on the debt?
The new CRA policy, resulting from their settlement agreement with the offices of the AG of several states, and also incorported into their National Consumer Assistance Plan, is that the CRA will unilaterally block posting of reported medical collections until at least 180 days has expired from the date of initial delinquency, thus providing time for possible resolution before it hits consumer credit reports.
If it has been less than 180 days since the asserted date of initial delinquency, it is possible that they have reported to a CRA, but the CRA is delaying showing in your credit report.
What is the asserted DOFD?
In addition to what @RobertEG has already said Don't be scared of it Get on top of it ASAP. I just had some of the same and I jumped on it and made arrangements to pay and they did not report it to the CRA because I handled it ASAP. Some medical collections will even delay reporting it if you make payment arrangements and autopay. I did this with about $30,000.00 worth of medical bills (had a heart issue in Feb/2018) some went to collections some i was able to keep inside the doctors office but the point is none of them reported a negative on my CR because I either paid it off or set up payment arrangements that i faithfully keep. Either way your in a good position to negotiate dealing with it before it turns into a major negative. Call them up and tell them you don't want this on you CR and how can you deal with this insuring it does not get reported. I have found that many medical collections agencies are more then willing to deal with you in a positive manner if you don't let it drag on until you force their hand.
Ask them if they posted it already and then negotiate to pay in full for them to delete any info they already reported and make sure you get that in writing before you pay them. If all of this is brand new chances are in your favor you will be successful in either not having it reported yet or getting them to remove anything they did report. I have done this with both medical and non medical collections. I just had a collections for a old wireless bill report and i paid it off in a 3 month payment plan the Collection Agency would not agree to a pay for delete however after I paid my final payment they informed me that even though they don't delete that, because it was only 3 months old they as a professional favor to me would go ahead and delete it and they did. Bottom line is you must communicate and determine what has and has not been done then make arrangements to pay it to where it's favorable to you. If your dealing with the original creditor (doctors) and they agree to take payment then they should also agree to recall the account from the collection agency (which should stop all collection efforts) otherwise you should be dealing with the collection agency and negotiating with them. Some companies will not even deal with you once they turn it over to a collections agency.
Also, If this bill should have been covered by medical insurance or was already paid by the same then you should be providing evidence of this and fighting being double charged and threatened by a collection agency without just cause.