Data analyzed are from a prospective cohort study comparing patients of a psychiatric hospital with a contract of a model project (model hospital) with patients of a psychiatric hospital without this type of contract as a control (control hospital). The observation time covers 20 months with primary data collection at recruitment (t0), at first follow-up after 10 months (t1), and at second follow-up after 20 months (t2) between May 2016 and October 2018.
Both psychiatric hospitals are located in North Rhine-Westphalia, a Federal Land in the central western part of Germany. They are equivalent in respect of structural features (inpatient care, day care, outpatient service, number of beds, staff, and patients treated), the spectrum of psychiatric diagnostic and treatment procedures provided, and both are responsible for the compulsory psychiatric care of the resident population in their official catchment area.
In the model hospital each patient is assigned to a continuous multi-professional treatment team that is responsible for this patient’s treatment over time, e.g., a new treatment contact after a year, and across all treatment sectors, i.e., inpatient, outpatient, and day care. Hereby a higher relational continuity shall be ensured to a patient within a sector, e.g., if a change of wards occurs, and when a patient changes between treatment sectors, e.g., if a patient stays in day-care or contacts the outpatient service.
The control hospital does not provide this structural therapeutic personnel feature. The staff is usually assigned to a defined therapeutic working setting in one sector, e.g., inpatient ward or outpatient clinic. But a patient can experience an ‘uncoordinated’ relational continuity in the control clinic due to staff rotation or substitution as well.
Patients treated in the psychiatric hospital of their catchment area usually continue their treatment with this hospital, either as inpatient, outpatient, or in day care, and outside office hours in emergency cases. But they can seek treatment in a hospital outside their catchment area or visit psychiatrists in their private practices.
Eligible for participation in the cohort study were all newly admitted inpatients, 18 years or older, during the recruitment period with a psychiatric diagnosis as defined by ICD-10 (F0 – F7) regardless of their health insurance.
Not eligible for participation in the cohort study were patients without written consent to participation and data collection, patients not capable of being surveyed, a hospital stay of less than 2 days, a residence outside the hospital’s catchment area, or lack of a permanent residence.
Recruitment lasted 6 months in both hospitals. During recruitment 1235 patients meeting inclusion criteria were admitted to the hospitals, but 228 (18.5%) of these patients met exclusion criteria. The remaining 1007 patients got invited to participate in the cohort study. 435 patients were able and agreed to participate in the cohort study. 323 of the participating patients of the cohort study had at least one following treatment contact after recruitment with the hospital and the continuity of care measure could be calculated. These 323 study patients were analyzed to answer the research question we address here.
All 435 participating patients of the cohort study were invited after 10 months, and after 20 months for a follow up interview conducted in the hospital. If a participating patient was hospitalized as inpatient or for day care at the time for follow-up the interview was offered and conducted in the hospital, all other participating patients were invited by letter and or telephone to schedule the follow-up with the psychiatrist or psychiatric resident of their treatment team at recruitment. The follow-up interview was completed (patient-rated questionnaires and basic documentation) by the study assistant.
Data on sociodemographic characteristics, diagnoses, and medical history were asked from the patient and completed from the patient clinical records.
The psychiatric diagnoses were diagnosed using the diagnostic criteria for research of the ICD-10 Classification of Mental and Behavioural Disorders  by trained psychiatrists as well as psychiatric residents and supervised by senior psychiatrists. Assignment to the main psychiatric diagnosis group was based on the dominant diagnosis at the time of recruitment according to the ICD-10 diagnostic criteria.
Continuity of care measure
The assessment of the continuity of care is based on the COC (continuity of care)-index according to Bice and Boxerman  who provided an operational definition of continuity of care for a quantitative measure. We adapted their concept to the specifics of the context and data availability of the study hospitals. Our continuity of care measure was defined, surveyed and calculated identically for all study patients. Treatment continuity was ensured in our operationalization if a treatment was carried out again by the responsible senior psychiatrist from the initial treatment team of the ‘continuous multi-professional treatment team’ in the model hospital or the treatment team in the respective setting in the control hospital. The initially responsible senior psychiatrist was identified by the patient’s discharge letter from the inpatient stay during recruitment. The responsible senior psychiatrist was identified in the same way for any further contact of the patient with the hospital by the patient’s following discharge letters from inpatient or day care stays or outpatient reports from outpatient contacts. Discharge letters and outpatient reports are written by the attending psychiatrist or psychiatric resident of the treatment team for which the senior psychiatrist is responsible. The senior psychiatrist corrects and signs discharge letters and outpatient reports which are integrated in the patient clinical records. All contacts were covered by discharge letters or outpatient reports.
The degree of care continuity was calculated dividing the number of all treatment contacts as inpatient, outpatient, or during day care with the initially responsible senior psychiatrist by the total number of all treatment contacts as inpatient, outpatient, or during day care of a patient in the hospital during the observation period. The resulting variable ‘continuity of care’ is a metric variable with values between 0 and 1 with 0 indicating no continuity of care in the contacts and 1 indicating all contacts were with the same treatment team. Outpatient contacts were only included if they took place during regular office hours from Monday through Friday between 8 and 17 o’clock. Emergency outpatient contacts outside of office hours were provided by the hospitals, but these contacts were not included in the calculation of the continuity of care measure because neither the hospital nor a patient could achieve continuity of care due to daily changes in the psychiatrists in charge.
Symptom severity was documented using the observer-rated Clinical Global Impression (CGI) rating scales  with possible scores ranging from 0–7 and with higher scores indicating higher symptom severity, functioning was documented using the observer-rated Global Assessment of Functioning (GAF) scale  with possible scores ranging from 1–100 and with higher scores indicating higher functioning, and health related quality of life was documented using the patient-rated Euro Quality of Life (EQ-VAS)  with possible scores ranging from 0–100 and with higher scores indicating higher quality of life. The outcome measures were collected at all three points in time. The observer-rated CGI and GAF scales were scored by the treating psychiatrist or psychiatric resident and the self-rated EQ-VAS was rated by the patient. The CGI as well as the GAF are part of the basic diagnostic procedures in both hospitals and psychiatrists and psychiatric residents are trained in rating.
To answer our research question on continuity of care and clinical outcome measures we analyzed all those participating patients of our cohort study with two or more treatment contacts in the observation period, hereinafter referred to as ‘study patients’. For analyses, the variable continuity of care was median-dichotomized to distinguish the study patients irrespective of their hospital status into two patient groups, patients with a higher degree of continuity of care and patients with a lower degree.
First, we describe the study patients by reporting mean and standard deviation respectively numbers and percentages, separately for the group of study patients with a higher degree of continuity of care and the group of study patients with a lower degree of continuity of care.
To investigate group differences between study patients with a higher and lower degree of continuity of care, the Mann–Whitney-U-test was used for interval-scaled data and the Chi2-test for nominal-scaled data. Significance level was set at 0.05.
We describe the differences between both groups for all study patients and separately for only those study patients who could be included with data for all three survey time points and the independent variables in at least one of the three analyses of variance for the outcome measures. An imputation procedure was not applied.
Finally, three analyses of variance with repeated measurements (three points in time) were developed for the association between the patient- (EQ-VAS) or observer-rated (CGI, GAF) outcome measures and continuity of care (median dichotomized) as between-subject factor controlling for the independent variables age (18 to 40 years, 41 to 55 years, older than 55 years), sex (female, male), migration background (with, without), main treatment diagnosis (psychoactive substance use (ICD-10 F1), general psychiatric disorders (ICD-10 F2-7)), duration of psychiatric disease (less than 1 year, 1 to 10 years, more than 10 years), and hospital (model hospital, control hospital).
All analyses were performed using IBM SPSS versions 26.