Usa la seconda forma della funzione :
Es.:
SELECT *
FROM crosstab(
$$
SELECT lab_tests_results.batch_id, lab_tests.test_name, lab_tests_results.test_result::FLOAT
FROM lab_tests_results, lab_tests
WHERE lab_tests.id=lab_tests_results.lab_test
AND (
lab_tests.test_name LIKE 'Test Name 1'
OR lab_tests.test_name LIKE 'Test Name 2')
ORDER BY 1,2
$$,
$$
VALUES('pH'), ('Temp')
$$
) AS final_result(batch_id VARCHAR, "pH" FLOAT, "Temp" FLOAT);