Count of unique study subjects in multiple studies

Last updated: 2023-08-31 08:33


As the reduction of administrative burden at side of data providers is part of Healthdata’s mission. Knowing the number of patients (study subjects) in their own study project that are in multiple study projects supported by (and thus available at data warehouse of, facilitates the reuse of data collected, instead of starting a new data collection to obtain that same information.

Based on the provided solution the client can decide whether it is feasible or not to link its own study project with other projects (i.c. “there are enough unique study subjects that are in both study projects”).

Linking of databases increases the reuse of data, reduces the need to start new data collections, and thus contributes to the reduction of administrative burden of the data providers. It is also less expensive compared with the creation of new data collections.

Through the HD4RES2 application Heathdata delivers a data table on daily bases which aims to provide the necessary insight on the business project common study subject. Those figures are available in the data table V_HDM_COMMON_SUBJ detailed below.


In SAS Enterprise Guide, the data table is accessible via the ‘Servers’ window, located at the bottom left.

First open the following path Servers >> SASAppRES >> Libraries >> HD4RES2

Then, open the following table "V_HDM_COMMON_SUBJ_CNT"

This data table contains the following fields:

HDBP1_codeCD_PROJ_BUSHD business project code (HDBPxxxx) of the base project
HDBP1_nameTX_PROJ_BUS_NAMEHD Project business name of the base project
HDBP1_abbreviationTX_PROJ_BUS_ABBREVHD Project business abbreviation of the base project
HDBP2_code CD_PROJ_BUS2HD business project code (HDBPxxxx) of the compared project
HDBP2_name TX_PROJ_BUS2_NAME Project business name of the compared project
HDBP2_abbreviation TX_PROJ_BUS2_ABBREV Project business abbreviation of the compared project
HD_ARCH_componentTX_ARCH_COMPONENTDatabase component/DWH layer
Count_DateD_COUNTDatepart of the metrics calculation timestamp (at 23:59:59)
CountMS_COMMON_SUBJCount of the total number of study records in common between the base and compared project
Count_NewMS_NEW_ COMMON_SUBJ New number of common study subjects as from previous date and time

Reference table: V_HDM_MAP_TBL_PROJ

As business projects/data collections often led to the creation of several data tables the figures are resulting from the consolidation of the most representative business project data tables. Consequently those data tables must be treated with respect to their own functional and structural properties.

To this end, researchers may consult an additional data table V_HDM_MAP_TBL_PROJ related to their project on the HD4RES2 application which describes the content and rules applied on each data table by business project.

In SAS Enterprise Guide, the data table is accessible via the ‘Servers’ window, located at the bottom left.

First open the following path Servers >> SASAppRES >> Libraries >> HD4RES2

Then, open the following table "V_HDM_MAP_TBL_PROJ"

FieldNameDescriptionUsed for dimension
TX_SCHEMA_NAMSchema location of the data table HD_ARCH_component
TX_TBL_NAMTable name of the data table
TX_REG_NAMHD internal DWH register nameHDBP_code
CD_PROJ_BUSHD Project business code (HDBPxxxx) HDBP_code
TX_PROJ_BUS_NAMEHD Project business code name
TX_PROJ_BUS_ABBREVHD Project business abbreviation
TX_SQL_DP_TPE Field or SQL statement used to identify the type of the data providerHCO_NIDHICode
TX_SQL_DP_VALField or SQL statement used to identify the data providerHCO_NIDHICode
TX_SQL_SUBJField or SQL statement used to identify the study subject
FL_INCL_METRIC_CNT_REC_PATFlag which indicates whether the table contributes toward the calculation of the metrics:
1, 2 => included in the figures calculation
0 => explicitly excluded from the calculation
null => implicitly excluded from the calculation
DT_VALID_FROMTimestamp as from when above properties are applicable
DT_VALID_TOTimestamp as to when above properties are discarded

Calculation of common study subject

One study subject is defined as the entity for which data has been collected. Depending the data collection most of the time a study subject represent the patient.

Because of the respect for privacy it is important to understand that each data collection set of data tables were build in such a way that it has been made impossible to users to link data of the same patient from different data collections. Consequently it will be impossible to reproduce the same figures as the table provides.

For every new eHealth patient identification key a new identification key PER patient and PER data collection is created. Because access to different data collections does not imply access to a combination of them, this eHealth identification key has been hidden from all the users of the data collections. Consequently to deliver the requested metric, we have at our disposal a table not accessible to the users, which provide the link between the initial eHealth patient identification and the data collection specific identification.

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