Diagnostic Trajectories in Primary Care at 12 Months: An Observational Cohort Study

Background: Little is known about the epidemiology of diagnosis in primary care.

Methods: A prospective observational cohort study was conducted of adults presenting between August and December 2018 to primary care clinics across two health systems with an undiagnosed medical problem. Primary outcomes were (1) likelihood of a definitive diagnosis by 12 months and (2) time to diagnosis. Multivariate logistic regression was used to assess for factors associated with the likelihood of reaching a diagnosis, and multivariable Cox regression was used to assess for factors associated with time to diagnosis. Bivariate models were used to explore unadjusted relationships between the cases' organ systems and likelihood of and time to diagnosis.

Results: Among 410 cases in a diverse patient population, 206 (50.2%) reached a final diagnosis within 12 months, with a median time to diagnosis of 5 days (interquartile range = 0-46). Among these cases, 32.4% reached a diagnosis within the first month. A majority of cases not diagnosed within a month of the first presentation remained undiagnosed at 12 months. The likelihood of diagnosis and time to diagnosis did not differ by clinician or patient characteristics, clinicians' level of diagnostic uncertainty, chronicity of the medical issue, or visit type. There were no significant associations between organ system and likelihood of time to diagnosis.

Conclusion: Patients presenting with new or unresolved problems in ambulatory primary care often remain undiagnosed after a year. There were no provider or patient-level variables associated with such lack of diagnosis. The causes, contributors, and consequences of lack of timely diagnosis and potential solutions require further research.