Distinguishing Clinical Observations and Medical Conditions

As the pharmaceutical industry moves quickly towards standardized clinical study data, I continue to see confusion in how clinical observations and medical conditions are represented. In clinical medicine there is a sharp distinction between these two concepts, yet in standardized study data submissions they are often lumped together.

A clinical observation is just that: someone observes a clinical symptom or sign of a patient. The observer may be the patient (in which case it's called a symptom) or someone else (in which case it's called a sign). Often a medical device is involved in the observation (blood pressure cuff, thermometer, x-ray, MRI, etc.). Often the observer follows a procedure to provide some level of consistency in making the observation. A headache, a rash, a fever, an elevated blood pressure, a low serum sodium, a round hyper intense lesion on an MRI are all examples of clinical observations.

Then we have medical conditions, which are diseases or injuries or other conditions that interfere with well-being. The Free Medical Dictionary defines a medical condition as:  A disease, illness or injury; any physiologic, mental or psychological condition or disorder (e.g., orthopaedic; visual, speech or hearing impairments; cerebral palsy; epilepsy; muscular dystrophy; multiple sclerosis; cancer; coronary artery disease; diabetes; mental retardation; emotional or mental illness; specific learning disabilities; HIV disease; TB; drug addiction; alcoholism). A biological or psychological state which is within the range of normal human variation is not a medical condition.  

This is a reasonable definition, although I disagree with the last sentence in that certain temporary  but normal physiologic states can be considered medical conditions. For example, I think pregnancy is a medical condition because, although it is within the range of normal human variation, it is a state that benefits from medical intervention (pre-natal care, obstetrical care) to minimize complications to the mother and child. 

Herein lies the major distinction between clinical observations and medical conditions. Clinical observations serve as input to an assessment (often conducted by a health care professional) to determine that a medical condition exists. Medical conditions are listed on a patient's problem list and are the focus of medical interventions. Clinical observations are not. 

Take for example an elevated blood pressure (clinical observation). Does this mean the patient has hypertension (medical condition)? Not necessarily. If the patient is obese, perhaps the wrong device was used. A normal sized cuff on an obese patient may give falsely elevated readings. Repeating the blood pressure measurement using a larger cuff may in fact reveal a normal blood pressure. It is also well known that anxiety of visiting the doctor may temporarily raise the blood pressure, so repeated measurements over time in a more relaxed setting could demonstrate normal serial blood pressures. 

Adverse Events are medical conditions temporally associated with a medical intervention. Here again, an assessment is necessary to determine that one or more observations indicate the presence of an adverse event. 

Study data standards continue to mix the two. In an earlier post, I described how BRIDG has the same problem. As another example, I was recently reviewing the Therapeutic Area User's Guide (TAUG) for Multiple Sclerosis. It advocates placing past clinical observations related to the MS diagnosis in the medical history (MH) domain. The past medical history portion of a typical history and physical evaluation is reserved for past medical conditions, not for past clinical observations. I think they should be separate. Unfortunately there is no good place in the SDTM to place past clinical observations.

Why keep them separate? Medical conditions have metadata that differ from clinical observations. For example, one may want to know which observations were used to identify the medical condition, who did the assessment, the date the medical condition began (i.e. the date of the earliest observation associated with the medical condition), the date of diagnosis (when the medical condition was first identified, which is often later than the onset date) etc. Was it associated with a medical intervention, and if so which ones? Is the medical condition considered adverse? From such a "medical condition" domain, one could derive AE, CE and MH.

I also think we need a single unambiguous way to represent all clinical observations, past and present. This is still lacking in clinical research, which results in multiple domains and new domains as data for more and more therapeutic areas are standardized. Key metadata for clinical observations are the date the observation was made, who made it, was it planned or unplanned, what procedure (if any) was used, what device (if any) was used, relevant metadata about the procedure/method/anatomic location, relevant metadata about the device, any associated observations (e.g. diastolic BP and systolic BP). We do not need an imaging domain, as others have suggested. Imaging is simply a method to obtain an observation.