> We considered 2 exposures of interest: 1) specific underlying medical conditions and 2) the number of conditions. We captured data on both exposures by using ICD-10-CM diagnosis codes from inpatient or outpatient hospital records in PHD-SR from January 2019 up to and including a patient’s first inpatient encounter for COVID-19. We used 1 encounter with an ICD-10-CM code to establish the presence of an underlying condition because few patients had multiple encounters in this hospital database. We excluded 3 ICD-10-CM codes (ie, oxygen support, dependence on a ventilator, and tracheostomy) listed during the patient’s COVID-19 encounter because they could be part of COVID-19 treatment.

...

> To further differentiate underlying conditions from acute complications of COVID-19, a panel of physicians (K.K.W., W.M.K., H.G.R., B.B., N.T.A., J.M.N.) classified the 314 CCSR categories into “likely underlying” (274 categories; eg, asthma); “indeterminate,” which could include underlying or acute complications or both (29 categories; eg, cardiac dysrhythmias); or “likely acute” (11 categories; eg, acute pulmonary embolism).

Am I reading this correctly that they are determining "likely underlying fear and anxiety disorder" from a single ICD-10 code that was likely generated at the time of admission for severe COVID-19? If that's correct, it seems rather flawed at determining if these people had an actual underlying anxiety condition or if the anxiety was due to severe COVID-19 symptoms(moderate to severe difficulty breathing, lack of sleep, lack of food/fluids and pain).

https://www.cdc.gov/pcd/issues/2021/21_0123.htm