Table 1.

Characteristics of a symptom vs a symptom cluster

Symptom*	Symptom cluster
	Same characteristics as a symptom—plus:
Subjective perception	Two or more concurrent symptoms
May vary over time	Stable group of symptoms
Has antecedents	Independent of other clusters
Influences outcomes	May have shared underlying mechanism(s)
May be influenced by an intervention	May have shared outcome(s)
Has an underlying mechanism	Temporal dimension

^*Symptoms are subjective sensations. Signs are objective indications of some medical characteristic.