The query below will pull what I need but pulls all obsvalues and I only want it to pull the most recent. The completeddate is probably what needs to be used in some sort of nested select but I'm not sure how to do this and return values for all rather than just values for one person.
SELECT distinct obsvalue, p.person_id, p.last_name, p.first_name, p.person_nbr, o2.completeddate
FROM order_ o2
INNER JOIN ncsuds_lab_test_desc d ON RTRIM(o2.actText) = RTRIM(d.test_desc) and d.order_ind = 'Y' AND d.selected_diag_id = 42
inner join person p on o2.person_id = p.person_id
WHERE o2.obsvalue IS NOT NULL
AND ISNUMERIC(o2.obsvalue) = 1
and o2.completeddate > '20150101'
order by completeddate desc