This page is part of the MII Implementation Guide PRO (v2027.0.0-ballot.1: 2027 Ballot 5) based on FHIR (HL7® FHIR® Standard) R4. This is the current published version in its permanent home (it will always be available at this URL). For a full list of available versions, see the Directory of published versions

PHQ-9

Clinical Context

The PHQ-9 is a validated screening instrument for depression with nine items. The instrument assesses the frequency of depression symptoms over a two-week period on a four-point scale.

Scoring and Interpretation:

• 0-4: No/minimal depression
• 5-9: Mild depression
• 10-14: Moderate depression
• 15-19: Moderately severe depression
• 20 and above: Severe depression

Clinical Notes: Item 9 assesses suicidal ideation and requires immediate clinical evaluation for any positive response, regardless of the total score.

FHIR Implementation

Language Strategy: The PHQ-9 is implemented with English as the primary language, as the original version of the instrument was written in English. German translations are provided as Translation extensions. This ensures correct validation against LOINC terminologies.

Questionnaire

Canonical URL: https://www.medizininformatik-initiative.de/fhir/ext/modul-pro/Questionnaire/mii-qst-pro-phq-9

Implemented Capabilities:

• Displayable, Collectable, Populatable, Calculatable, Extractable, Domain-aligned

Key Features:

• Automatic score calculation via FHIRPath: %resource.item.where(linkId.matches('^phq-.*-q0[1-9]$')).answer.value.weight().sum()
• Populatable capability for server-side calculations implemented
• LOINC-coded answer options

See the Questionnaire definition for the full resource.

Score Representation

The PHQ-9 score is represented at multiple levels:

1. As a calculated item in the QuestionnaireResponse (linkId: phq9-total-score)
2. As an Observation with LOINC code 44261-6 "PHQ-9 total score"
3. As a domain score mapped to PROMIS Depression T-Score

ObservationDefinition: mii-obsdef-pro-phq9-score

• Defines value range: 0-27 {score}
• Specifies interpretation guidelines

Domain Mapping

The PHQ-9 can be mapped to PROMIS Depression T-Scores:

PHQ-9 Score	PROMIS T-Score	Interpretation
0-4	~41.0	Minimal
5-9	~50.0	Mild
10-14	~60.0	Moderate
15-19	~70.0	Moderately severe
20-27	~77.5	Severe

Example Resources

PHQ-9 QuestionnaireResponse

See the full example.

Validation

Technical: Score range 0-27, all items required for a valid score, ordinal values: 0, 1, 2, 3

Clinical: Sensitivity 88%, specificity 88% for major depression (cut-off 10 and above), test-retest reliability: 0.84

References

Kroenke K, Spitzer RL, Williams JB. The PHQ-9: validity of a brief depression severity measure. J Gen Intern Med. 2001;16(9):606-13.