Dose syntax implementation guidance for FHIR STU3

This guidance is under active development by NHS Digital and content may be added or updated on a regular basis.

Step 3 - Order the list of VMPs in a clinically suitable order

Function for ranking / ordering

Uses the FNC_CALC_QTY function from above then calculates a ranking value which can be used to order the overall SQL query.

FUNCTION FNC_CALC_RANK( doseQty DECIMAL(9,3)
                      , numerator DECIMAL(30,12)
                      , denominator DECIMAL(9,3)
                      , unitDoseFormStrength DECIMAL
                      , formId BIGINT UNSIGNED
                      )
RETURNS SMALLINT(5) UNSIGNED

BEGIN
	DECLARE v_qty DECIMAL(30,12) UNSIGNED;
	DECLARE v_rank SMALLINT UNSIGNED;
	DECLARE v_divisable BIGINT UNSIGNED;

	SET v_qty = FNC_CALC_QTY(doseQty, numerator, denominator, unitDoseFormStrength);

	IF ( v_qty < 1 ) 
            THEN SET v_rank = 3;
	ELSE IF ( ( v_qty % 1 ) != 0 )
            THEN  SET v_rank = 2;
	ELSE 
	   SET v_rank = 1;
	END IF;

	IF ( v_rank != 1 )
            THEN SELECT name
                   FROM lookup
                  WHERE valueset = "NOTDIVISABLE"
                    AND id = formid 
                   INTO v_divisable;
	
            IF ( NOT NULL(v_divisable) ) 
                THEN SET v_rank = 4; 
            END IF;
	END IF;

	RETURN v_rank;
END

Where formid is the dm+d code for the requested dose quantity unit of measure.

The rules for the ranking are best shown in a table.

Calculated Quantity Ranking Ranking Reason
Integer 1 Can be fulfilled by one or more complete doses
Decimal greater than 1 2 Requires a number of doses include part doses
Decimal less than 1 3 Requires part of a a single dose
Decimal using a dose form typically not divisable 4 Unlikely to the clinically safe to use this product

Identification of dose forms that are typically not divisable

The following dose forms are typically not divisible, however this is not always the case.

For example there are some modified-release tablets with a score along the centre to aid division, but in most cases, modified-release products should not be divided.

The same applies for products as capsules. These represent the more common dose forms used within dm+d concepts. Other non-divisible dose forms may exist but their use would be rare, but this reference table can be extended or customised as required for a local implementation.

SNOMED / dm+d code Dose Form
385049006 Capsule
385054002 Modified-release capsule
385061003 Modified-release tablet
421720008 Spray

Complete Stored Procedure

PROCEDURE PRC_VTM_TO_VMP( IN IN_vtm_id BIGINT UNSIGNED
                        , IN IN_dose_qty DECIMAL
                        , IN IN_dose_uom_cd BIGINT UNSIGNED
                        , IN IN_form_id BIGINT UNSIGNED
                        , IN IN_route_id BIGINT UNSIGNED
                        )
BEGIN
	SELECT DISTINCT vmp.vmpid
        , vmp.name
        , FNC_CALC_QTY( IN_dose_qty
                      , FNC_CONVERT_UNITS( vpi.strnt_nmrtr_val
                                         , vpi.strnt_nmrtr_uomcd
                                         , IN_dose_uom_cd
                                         )
                      , vpi.strnt_dnmtr_val,vmp.udfs
                      ) AS qty
        , vmp.udfs_dose_uomcd
        , vpi.strnt_dnmtr_uomcd
        , FNC_CALC_RNAK( IN_dose_qty
                       , FNC_CONVERT_UNITS( vpi.strnt_nmrtr_val
                                          , vpi.strnt_nmrtr_uomcd
                                          , IN_dose_uom_cd
                                          )
                       , vpi.strnt_dnmtr_val
                       , vmp.udfs,vmpform.formid
                       ) AS rnk
	  FROM vtm 
	 INNER JOIN vmp 
       ON ( vtm.vtmid = vmp.vtmid )
	 INNER JOIN vmpform
       ON ( vmp.vmpid = vmpform.vmpid )
	 INNER JOIN vmproute
       ON ( vmp.vmpid = vmproute.vmpid )
	 INNER JOIN vpi
       ON ( vmp.vmpid = vpi.vmpid )
	 INNER JOIN lookup
       ON ( vpi.strnt_nmrtr_uomcd = lookup.id )
	 WHERE vtm.vtmid = IN_vtm_id
	   AND ( vmpform.formid = IN_form_id OR ISNULL(IN_form_id) )
	   AND ( vmproute.routeid = IN_route_id OR ISNULL(IN_route_id) )
	 ORDER BY rnk ASC
        , qty ASC;
END
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