Valued Westpac Labs Client and Care Provider,

Below, please find a few recommendations about ordering the most appropriate tests to improve the accuracy and the turnaround time of our laboratory services. Ordering the right test for the right reason is good stewardship and will result in the best service to our patients.

Vitamin D Testing

Vitamin D, a group of fat-soluble prohormones, is an essential Vitamin. Vitamin D is stored in the human body as calcidiol (25-hydroxy vitamin D). Serum concentration of 25-hydroxy vitamin D (order code: E751) is the best indicator of Vitamin D status. On the other hand, Vitamin D, 1,25-dihydroxy is primarily indicated during patient evaluations for hypercalcemia and renal failure. Vitamin D, 1,25-dihydroxy should not be ordered in addition to, or in lieu of Vitamin D, 25-hydroxy for Vitamin D deficiency testing. Vitamin D test orders are often subject to CMS reviews and hence ordering the correct tests and documenting the indication on the patients’ chart is paramount. 

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Syphilis Screening

Syphilis screening may be done using the traditional or the reverse algorithm. Both algorithms contain a treponemal and a non-treponemal test. The traditional algorithm tests VRDL or RPR first and reflexes to a treponema specific antibody assay. The reverse algorithm starts with a highly accurate antibody assay and reflexes to RPR and titer to determine the activity of the disease. When using the reverse algorithm, if the nontreponemal test (RPR) is negative, this is considered a discrepant result. The laboratory should perform a treponemal test different from the one used for initial testing, preferably TP-PA to adjudicate the results of the initial test. To achieve the highest accuracy and fastest turnaround time, we recommend the reverse algorithm (order code: F204) which starts with TP antibody screen and reflexes to RPR and titer. If the results are discrepant, Treponema TP-PA test will be ordered. TP-PA test should not be used by itself for screening. TP-PA test is manual and labor-intensive and should be reserved as a confirmatory test. For further information please visit

Acute HSV Infection

Diagnosing acute HSV infection requires identification of the virus or viral DNA from the lesion. CDC does not recommend using serology test for acute herpes infection. HSV IgM is non-specific and often cross reacts with IgG or other viral antibodies. CDC recommends HSV NAAT (PCR) testing from a swab of the ulcer or mucocutaneous lesion. HSV culture, Tzanck preparation, and direct anti-fluorescent techniques lack sensitivity and are not recommended. WestPac labs will discontinue offering HSV culture on July 1st, 2022. HSV 1 and 2 PCR (order code: U954) is available and is recommended for any site using the Eswab transport media.

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Thank you for your collaboration in optimizing testing for our patients. If you have any questions, please reach out to Dr. Zoltan Nagymanyoki M.D, Ph.D., MBA, medical director via email at