Add documentation for counting patients with high blood pressure

Care/Clinical/count_of_patients_with_high_bp.md

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+
+# Count of Patients with High BP
+
+> Count of patients whose latest recorded systolic blood pressure is greater than 140
+
+## Purpose
+
+Counts patients whose most recent recorded systolic blood pressure from the specified questionnaire is above `140`.
+
+## Parameters
+
+| Parameter | Type | Description | Example |
+|-----------|------|-------------|---------|
+| `date_filter` | DATE / range | Metabase date filter (typically bound to `emr_questionnaireresponse.created_date`) | `'2026-08-01'` |
+
+---
+
+## Query
+
+```sql
+WITH latest_sbp AS (
+		SELECT DISTINCT ON (emr_questionnaireresponse.patient_id)
+					 emr_questionnaireresponse.patient_id AS patient_id,
+					 (answer_element->>'value')::numeric AS systolic_bp
+		FROM emr_questionnaireresponse
+		CROSS JOIN LATERAL jsonb_array_elements(emr_questionnaireresponse.responses) AS response_element
+		CROSS JOIN LATERAL jsonb_array_elements(response_element->'values') AS answer_element
+		WHERE emr_questionnaireresponse.status = 'completed'
+			AND emr_questionnaireresponse.questionnaire_id IN (115)
+			AND response_element->>'question_id' = '66464c74-fee5-4a08-9283-f811564a06fb'
+			--[[AND {{date_filter}}]]
+		ORDER BY emr_questionnaireresponse.patient_id, emr_questionnaireresponse.created_date DESC
+)
+SELECT COUNT(*) AS patients_with_systolic_bp_gt
+FROM latest_sbp
+WHERE latest_sbp.systolic_bp > 140;
+```
+
+## Notes
+
+- **Hardcoded IDs:**
+	- `questionnaire_id = 115` identifies the blood pressure questionnaire.
+	- `question_id = '66464c74-fee5-4a08-9283-f811564a06fb'` identifies the systolic blood pressure field.
+	Update these if the form configuration changes.
+- **Metabase filter:** `[[AND {{date_filter}}]]` is a field filter — bind it to `emr_questionnaireresponse.created_date`.
+
+*Last updated: 2026-08-11*