Guides & Publications

 

Collection Guides & Test Information

As leaders in our field, we are always working to bring you the very latest in pathology testing technology.

The COVID-19 Sample Collection guide provides guidance on Swab options and Collection methods currently available to Medical practitioners. Western Diagnostic Pathology recommends collection for COVID-19 based on the current clinical advice and stock limitations.

The Test Reference Manual contains an overview of Western Diagnostic Pathology and the services that we provide to Medical Practitioners and their patients. In the manual, Medical Practitioners will find comprehensive listings on every test that Western Diagnostic Pathology can perform, an overview of each department and its collection requirements.

The Swab and Tube Collection guides contain an overview of Western Diagnostic Pathology collection processes required by Medical Practitioners and their patients.

We have changed the way we perform CT/NG testing and this means a change to the way samples are collected. Chlamydia trachomatis / Neisseria gonorrhoeae, HPV (Human papillomavirus), and TV/MG (Trichomonas vaginalis / Mycoplasma genitalium) on a single, fully-automated instrument. To support this change, we need to make adjustments to the collection process for CT/NG testing. For further information on the Collection Process, please see the documents for download below or contact your Medical Liaison Officer.

Please check expiry date of Thin Prep vials, which is in US format: year – month – day.

Changes to cervical screening in Australia

The medical community now has a greater understanding of cervical cancer as well as access to improved technology that will further reduce cervical cancer rates.
As a result of these developments, changes have been made to cervical tests nationwide. On December 1, 2017 the two yearly pap smear was replaced by a five yearly cervical screening. For further information on the new screening protocols, please see the documents for download below or call (02) 9005 7000.

As of July 1st 2022, there has been an update on the screening pathway in regards to the intermediate risk patients. Please refer to the Cervical Screening Test Guide and Flowchart. For more information please click here.

An update on self-collection testing

We will now accept self-collected samples that meet the strict Medicare criteria. Any samples that don’t meet the criteria will not be accepted. There is no privately billed service for these samples. Eligible samples will be sent to Victorian Cytology Service to perform testing. Additionally, all samples will need to be taken using the dry flocked swab. The request form must also clearly indicate Self-collect, Cervical screening test.
Please see MBS item 73071 for details on eligibility criteria and collection instructions.

Increasing cervical screening adherence for women

We are proud to support the Australian Cervical Cancer Foundation’s Comfort Checklist for cervical screening. The ACCF ‘Comfort Checklist’ aims to empower women by helping them overcome any emotional, cultural and physical barriers and encourage regular cervical screening.
For more information please click here.

ThinPrep test demonstration video

To keep you up to date with the cervical screening changes, we’ve put together a four minute video demonstrating how to use the ThinPrep Pap Test. This video will also outline why ThinPrep is our preferred Liquid Based Cytology test. If you have any questions, please feel free to contact one of our Medical Liaison Officers, or reach out to your local lab manager. We’re always happy to help. 
You can view the video here.

Through our specialist genomic testing laboratory Genomic Diagnostics, Western Diagnostic Pathology offers an extensive range of genetic tests to help in the diagnosis, treatment and monitoring of disease. Our testing menu spans from simple to complex and includes diagnostic and carrier testing for inherited disease, testing for somatic mutations in cancer, and pharmacogenetic testing using genetic and genomic techniques.

Our genetic diagnostic service is supported by:

Genetic testing is available for many disorders including:
Our comprehensive cytogenetic service is available for prenatal, postnatal and haematological malignancy testing using both conventional and molecular cytogenetic techniques. The requirements and costs can vary for each molecular test. Some testing may be rebateable if subject to Medicare guidelines and criteria. Other tests may incur an out of pocket charge.
For further enquiries including clinical enquiries, testing availability, collection requirements and costs please click below to visit the Genomic Diagnostics website:

Non-invasive Prenatal Testing (NIPT) is a revolutionary advance in prenatal screening. A simple and highly accurate blood test, NIPT screens for common chromosomal abnormalities from as early as the 10th week of pregnancy, for both singleton and twin pregnancies. Visit our specialist genomic testing laboratory Genomic Diagnostics for more information.

Thyroid function tests in pregnancy

In the first trimester, thyroid stimulating hormone (TSH) is often lower than in the non-pregnant state. This is mostly because of the TSH-like effects of beta-HCG. In the second and third trimester, as beta-HCG decreases, TSH is generally closer to non-pregnant levels. Free thyroid hormones (FT3 and FT4) are often lower in pregnancy, owing to changes in circulating binding proteins.

Different assays can give slightly different results, and therefore may have different reference intervals from one another in both pregnant and non-pregnant individuals.

Reference intervals for TSH in pregnancy

Reference intervals for TSH in pregnant patients measured by the Siemens Centaur platform used at Western Diagnostic Pathology are:

Trimester

Lower reference limit

Upper reference limit

1st

0.05 mU/L

3.5 mU/L

2nd

0.40 mU/L

4.0 mU/L

3rd

0.40 mU/L

4.0 mU/L

Increased TSH in pregnancy

The approach to subclinical hypothyroidism in pregnancy differs between various guidelines and local clinician preferences. This is due to the incompleteness of clinical trial evidence to support thyroid hormone replacement improving obstetric and neonatal outcomes in this setting. Guidelines also differ in the weighting placed upon TPO antibody status to guide treatment decisions.

In general, with the above caveats:

TSH

Recommendation

≥ 10 mU/L

Thyroid hormone replacement is indicated, irrespective of TPO antibodies or FT4

URL – 10 mU/L

Thyroid hormone replacement is generally indicated. TPO antibody status may help to inform this decision, and the need for thyroid hormone replacement post-partum

2.5 mU/L – URL

Thyroid hormone replacement is usually not indicated, although it may be considered in women with positive TPO antibodies

< 2.5 mU/L

Thyroid hormone replacement is not indicated, irrespective of TPO antibodies

URL: Pregnancy-specific upper reference limit, as defined above.

Established hypothyroidism in pregnancy

For women with established hypothyroidism on thyroid hormone replacement, requirements can increase during pregnancy. The target TSH in most cases is around 2 mU/L.

Decreased TSH in pregnancy

Hyperthyroidism in pregnancy is associated with adverse obstetric and neonatal outcomes. Women with TSH below the trimester-specific lower reference limit should have repeat TSH measurement with FT4 and FT3, to distinguish overt hyperthyroidism (in which FT4 and/or FT3 are increased, and TSH is usually below the reporting limit) from subclinical hyperthyroidism (in which FT4 and FT3 are within their respective reference intervals). Measurement of thyroid stimulating immunoglobulin (TSI; also called TRAB) is important to distinguish Graves’ disease from other causes. All pregnant women with overt hyperthyroidism should be reviewed by an endocrinologist, obstetric physician or related specialist.

If further information on thyroid function tests in pregnancy is required, doctors are welcome to contact the Chemical Pathologist at Western Diagnostic Pathology on 08 9317 0999.

References and further reading

Hamblin PS, Sheehan PM, Allan C et al. Subclinical hypothyroidism during pregnancy: the Melbourne public hospitals consensus. Internal Medicine Journal 2019; 49: 994-1000. Available from (abstract only): https://onlinelibrary.wiley.com/doi/pdf/10.1111/imj.14210

Alexander EK, Pearce EN, Brent GA et al. 2017 Guidelines of the American Thyroid Asssociation for the diagnosis and management of thyroid disease during pregnancy and the postpartum. Thyroid 2017; 27: 315-389. Available from: https://www.liebertpub.com/doi/pdfplus/10.1089/thy.2016.0457

Smith A, Eccles-Smith J, D’Emden M, Lust K. Thyroid disorders in pregnancy and postpartum. Australian Prescribe 2017; 40: 214-219. Available from: https://www.nps.org.au/australian-prescriber/articles/thyroid-disorders-in-pregnancy-and-postpartum

Medici M, Korevaar TI, Visser WE et al. Thyroid function in pregnancy: what is normal? Clinical Chemistry 2015; 61: 704-713. Available from: http://clinchem.aaccjnls.org/content/61/5/704

HbA1c – Diagnostic threshold and treatment targets

HbA1c (or glycated haemoglobin) refers to a fraction of haemoglobin that has been modified by the presence of glucose over the lifespan of the red blood cell (around 120 days). Higher average blood glucose concentrations are reflected by higher HbA1c.

HbA1c for the diagnosis of diabetes mellitus

An HbA1c ≥ 6.5% or 48 mmol/mol is consistent with a diagnosis of diabetes mellitus.

Medicare will provide a patient rebate for one diagnostic HbA1c per annum.

In patients without typical symptoms of diabetes mellitus, two positive tests are required to confirm the diagnosis (i.e. in addition to an initial HbA1c result ≥ 6.5%, a repeat HbA1c ≥ 6.5%, a fasting blood glucose > 7.0 mmol/L, or a blood glucose > 11.0 mmol/L two hours after a 75 g glucose load). 

HbA1c is not a suitable stand-alone diagnostic test for gestational diabetes or type 1 diabetes mellitus.

HbA1c for monitoring diabetes mellitus

In patients with established diabetes mellitus, treatment targets should be individualised based on a range of factors. A “general” target for most patients is ≤ 7.0% or 53 mmol/mol.  Patient groups in whom less stringent targets may be considered include those at higher risk of hypoglycaemia, older patients or those with comorbidities, and the very young. More stringent targets may be used in patients with type 2 diabetes mellitus of shorter duration. Further information is available in this Position statement of the Australian Diabetes Society.

In women with pre-existing diabetes mellitus planning pregnancy, an HbA1c target of < 6.5% is advocated to reduce the risk of fetal malformations, provided that the risk of hypoglycaemia in the individual patient is deemed to be sufficiently low when aiming for this target. Further information is available in this Position Statement of the Australian Diabetes in Pregnancy Society.

Medicare will provide a patient rebate for HbA1C when used in monitoring known diabetes four times per annum. Stating whether the patient has diabetes on the request form will help the patient to avoid receiving a bill.

“At target” does not always mean good glycaemic control

As with any laboratory test, meaningful interpretation can only be made in the overall clinical context. For example, whilst an “at target” HbA1c (e.g. 6.0%) in a patient with diabetes mellitus could indicate excellent glycaemic control, poorly controlled diabetes with frequent, alternating hypoglycaemia and hyperglycaemia over a period of weeks or months could also cause this result.

Causes of clinically misleading HbA1c results

While the most important contributor to HbA1c is blood glucose, several factors can cause increases or decreases in HbA1c which may be clinically misleading:

Misleading high HbA1c
Misleading low HbA1c

Iron deficiency anaemia

Haemolytic anaemia

Splenectomy

Recent acute blood loss

Recent steroid therapy, surgery or illness

Recent red blood cell transfusion

Certain haemoglobin variants

Iron, B12 and erythropoietin administration

 

Alcohol excess

 

Chronic kidney disease

 

Certain haemoglobin variants

Measurement issues and identification of haemoglobin variants

The method of measurement for HbA1c at Western Diagnostic Pathology is high-performance liquid chromatography. This method enables us to identify possible haemoglobin variants which may (1) cause misleading HbA1c results; (2) have possible inherent clinical significance; or (3) be of no significance at all. Sometimes we will provide a comment advising that a variant has been detected; haemoglobin electrophoresis may be recommended. If we are concerned about possible analytical interference, we may need to perform additional testing, which may cause a delay in reporting of the result.

Authors:

Dr Johan Conradie FRCPA (HOD)

Dr Melissa Gillett FRACP FRCPA

Dr Michael Page FRCPA

Dr Ranita Siru FRACP (Registrar)

Department of Clinical Biochemistry

Western Diagnostic Pathology

(08) 9317 0999

References and further reading

D’Emden MC, Shaw JE, Colman PG et al. The role of HbA1c in the diagnosis of diabetes mellitus in Australia. Med J Aust 2012; 197: 220-221. Available from: https://www.mja.com.au/journal/2012/197/4/role-hba1c-diagnosis-diabetes-mellitus-australia

Wah Cheung N, Conn JJ, d’Emden MC et al. Position statement of the Australian Diabetes Society: individualisation of glycated haemoglobin targets for adults with diabetes mellitus. Med J Aust 2009; 191: 339-344. Available from: https://www.mja.com.au/journal/2009/191/6/position-statement-australian-diabetes-society-individualisation-glycated