SQL Server 2008: Using Multiple dts Ranges to Build a Set of Dates - sql

Question

I'm trying to build a query for a medical database that counts the number of patients that were on at least one medication from a class of medications (the medications listed below in the FAST_MEDS CTE) and had either:
1) A diagnosis of myopathy (the list of diagnoses in the FAST_DX CTE)
2) A CPK lab value above 1000 (the lab value in the FAST_LABS CTE)
and this diagnosis or lab happened AFTER a patient was on a statin.
The query I've included below does that under the assumption that once a patient is on a statin, they're on a statin forever. The first CTE collects the ids of patients that were on a statin along with the first date of their diagnosis, the second those with a diagnosis, and the third those with a high lab value. After this I count those that match the above criteria.
What I would like to do is drop the assumption that once a patient is on a statin, they're on it for life. The table edw_dm.patient_medications has a column called start_dts and end_dts. This table has one row for each prescription written, with start_dts and end_dts denoting the start and end date of the prescription. End_dts could be null, which I'll take to assume that the patient is currently on this medication (it could be a missing record, but I can't do anything about this). If a patient is on two different statins, the start and ends dates can overlap, and there may be multiple records of the same medication for a patient, as in a record showing 3-11-2000 to 4-5-2003 and another for the same patient showing 5-6-2007 to 7-8-2009.
I would like to use these two columns to build a query where I'm only counting the patients that had a lab value or diagnosis done during a time when they were already on a statin, or in the first n (say 3) months after they stopped taking a statin. I'm really not sure how to go about rewriting the first CTE to get this information and how to do the comparison after the CTEs are built. I know this is a vague question, but I'm really stumped. Any ideas?
As always, thank you in advance.
Here's the current query:
WITH FAST_MEDS AS
(
select distinct
statins.mrd_pt_id, min(year(statins.order_dts)) as statin_yr
from
edw_dm.patient_medications as statins
inner join mrd.medications as mrd
on statins.mrd_med_id = mrd.mrd_med_id
WHERE mrd.generic_nm in (
'Lovastatin (9664708500)',
'lovastatin-niacin',
'Lovastatin/Niacin',
'Lovastatin',
'Simvastatin (9678583966)',
'ezetimibe-simvastatin',
'niacin-simvastatin',
'ezetimibe/Simvastatin',
'Niacin/Simvastatin',
'Simvastatin',
'Aspirin Buffered-Pravastatin',
'aspirin-pravastatin',
'Aspirin/Pravastatin',
'Pravastatin',
'amlodipine-atorvastatin',
'Amlodipine/atorvastatin',
'atorvastatin',
'fluvastatin',
'rosuvastatin'
)
and YEAR(statins.order_dts) IS NOT NULL
and statins.mrd_pt_id IS NOT NULL
group by statins.mrd_pt_id
)
select *
into #meds
from FAST_MEDS
;
--return patients who had a diagnosis in the list and the year that
--diagnosis was given
with
FAST_DX AS
(
SELECT pd.mrd_pt_id, YEAR(pd.init_noted_dts) as init_yr
FROM edw_dm.patient_diagnoses as pd
inner join mrd.diagnoses as mrd
on pd.mrd_dx_id = mrd.mrd_dx_id
and mrd.icd9_cd in
('728.89','729.1','710.4','728.3','729.0','728.81','781.0','791.3')
)
select *
into #dx
from FAST_DX;
--return patients who had a high cpk value along with the year the cpk
--value was taken
with
FAST_LABS AS
(
SELECT
pl.mrd_pt_id, YEAR(pl.order_dts) as lab_yr
FROM
edw_dm.patient_labs as pl
inner join mrd.labs as mrd
on pl.mrd_lab_id = mrd.mrd_lab_id
and mrd.lab_nm = 'CK (CPK)'
WHERE
pl.lab_val between 1000 AND 999998
)
select *
into #labs
from FAST_LABS;
-- count the number of patients who had a lab value or a medication
-- value taken sometime AFTER their initial statin diagnosis
select
count(distinct p.mrd_pt_id) as ct
from
mrd.patient_demographics as p
join #meds as m
on p.mrd_pt_id = m.mrd_pt_id
AND
(
EXISTS (
SELECT 'A' FROM #labs l WHERE p.mrd_pt_id = l.mrd_pt_id
and l.lab_yr >= m.statin_yr
)
OR
EXISTS(
SELECT 'A' FROM #dx d WHERE p.mrd_pt_id = d.mrd_pt_id
AND d.init_yr >= m.statin_yr
)
)

Answer 1

You probably don't need to select all of your CTE defined queries into temp tables.
I think that the query you're after has the form:
WITH FAST_MEDS(PatientID, StartDate, EndDate) AS
(
--your query for patients on statins, projecting the patient ID and the start/end date for the medication
),
FAST_DX(PatientID, Date) AS
(
--your query for patients with certain diagnosis, projecting the patient ID and the date
),
FAST_LABS(PatientID, Date) AS
(
--your query for patients with certain labs, projecting the patient ID and the date
)
SELECT PatientID
FROM FAST_MEDS
WHERE PatientID IN (SELECT PatientID FROM FAST_DX WHERE Date BETWEEN StartDate AND EndDate OR EndDate IS NULL AND StartDate < Date)
OR PatientID IN (SELECT PatientID FROM FAST_LABS WHERE Date BETWEEN StartDate AND EndDate OR EndDate IS NULL AND StartDate < Date)