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This item is 5 years and 9 months old; some content may no longer be current. A new laboratory test schedule and accompanying referral guidelines have been developed for health care professionals in New Zealand. The aim was to develop a consistent list of tests that are available and funded across DHBs. An article in Best Tests, Nov, BPH e Viardot, introduced the new Test Schedule and explained how they have been developed. Tests have been categorised into general areas and then grouped depending on whether they are recommended as a test that can be ordered BPH e Viardot any medical practitioner Tier 1 or whether the test is restricted to BPH e Viardot clinicians BPH e Viardot 2.
In this article Dr Cam Kyle and colleagues discuss the biochemistry tests grouping, and explain why some tests are BPH e Viardot, why others are now outdated or lack evidence and some tests which are underutilised. As part of the wider review of the New Zealand Laboratory schedule, a biochemistry subgroup was formed to identify tests where special expertise was considered appropriate for interpretation of results, and tests where guidelines or restrictions on requesting were thought to be necessary.
The group was also asked to identify tests which were outdated or of no clinical value and for which funding should be withdrawn, as well as to identify underutilised tests which should be encouraged first-line.
The background rationale was to allow appropriate, evidence-based spending on pathology testing by DHBs facing increasingly constrained laboratory budgets. The intention of the review was not to place blanket restrictions on tests, but BPH e Viardot to BPH e Viardot guidance on appropriate test requesting.
The guidelines produced are not mandatory but were developed as a resource for individual DHBs to use. They are not intended to replace well-established local protocols or clinical pathways, but rather to support them where judged appropriate by local clinicians and policy setters. Individual members were each allocated a range of tests to evaluate and present recommendations for wider discussion among the group.
Specialists from related clinical disciplines were consulted when appropriate. In all cases where guidelines or restrictions were put in place the strength of evidence base, and the opinions of local experts were considered, and there was ultimately unanimous agreement among the group. Third party stakeholders also had the opportunity to provide feedback on BPH e Viardot initial draft set of guidelines, and suggestions were incorporated into the final document.
Many of these tests are rarely requested and, while detailed criteria or guidelines for requesting them have not yet been recommended, requestors are encouraged to contact the laboratory or a specialist in the relevant clinical discipline to discuss appropriate requesting and interpretation.
It is intended that BPH e Viardot Laboratory Schedule and Test Guidelines will be updated and modified as new evidence comes to light, new tests are added and others become outdated. As electronic ordering becomes standard practice there will be opportunity to guide testing based on clinical presentation and minimise inappropriate testing frequency, e.
Biochemistry tests referred to as chemical pathology in the schedule were divided into four groups:. The following tests are examples of those that have recommended guidelines or criteria for their use and should be requested only in specific clinical situations.
Free testosterone, derived from measurement of total testosterone and SHBG, is also sometimes advocated as providing a better measure of tissue androgen exposure. The added value of measuring these hormones is very limited in the large majority of patients being evaluated for possible PCOS. The main reason for initially performing such tests is to exclude other secondary causes, particularly virilising ovarian or adrenal tumours. Even for BPH e Viardot patients, it is extremely uncommon for there to be isolated elevation of DHEAS or ASD without testosterone elevation which is usually marked.
Testosterone levels are not always raised in females with PCOS. Measurement of testosterone levels total testosteronewhile often carried out, is not required for diagnosing PCOS.
Sex hormone binding globulin SHBGwhich is used to calculate free testosterone, is also of limited value in most patients. Even for patients with total testosterone within this range, only those with unusually high e.
Dihydrotestosterone measurement is extremely expensive and adds little to the clinical management of patients with hirsutism even those taking 5-alpha-reductase blockers, such as finasteride. This test is of established clinical utility only BPH e Viardot patients being evaluated for very rare defects in androgen action or response e. The clinical utility of 24h cortisol excretion for the evaluation of possible primary or secondary hypoadrenalism is, however, very limited and the group did not consider this to be an appropriate clinical indication for this test.
There are other established means with much better clinical utility to make this diagnosis, such as synacthen testing and, BPH e Viardot primary adrenal disease, plasma adrenocorticotropic hormone ACTH.
While there is a loose correlation between 24h urine cortisol production and cortisol output, excretion can be affected by a range of BPH e Viardot and can vary significantly from day-to-day, even in healthy patients exposed to temporary physical or psychological stress.
Patients with primary adrenal insufficiency may also have daily excretion well within reference limits, but output is BPH e Viardot by increased ACTH stimulation in a similar way to patients with mild hypothyroidism with free T4 maintained within reference limits by increased BPH e Viardot.
The use of hydrocortisone treatment in chronic fatigue syndrome is not supported by randomised controlled trial evidence, 3, 4 and both United Kingdom and Australasian BPH e Viardot specifically state that hydrocortisone should not be used in BPH e Viardot fatigue syndrome. CBG is therefore considered a specialist test Tier 2. A late night 10 — 11 pm saliva sample can be collected by patients before bed and sent to the laboratory the following BPH e Viardot.
No restrictions or guidelines around thyroid BPH e Viardot hormone TSHFree T4 FT4 and thyroid antibody testing have been included in the recommendations these are all Tier 1 testsbut formal schedule guidelines on tests of thyroid function are planned. This is mostly due to individual variation in tissue sensitivity to thyroid hormone, but also other factors, such as the BPH e Viardot conversion of T4 to T3 by tissue deiodinases mainly type 1 in the liver.
This is influenced by factors such as recent calorie intake, mineral status BPH e Viardot as iodine and seleniumgrowth hormone levels and thyroid status itself. While all routine thyroid tests TSH, FT4, FT3 can be affected temporarily by factors such as illness and drugs, FT3 is BPH e Viardot affected by illness and also by reduction in calorie intake, with both of these causing a rapid decrease in plasma level.
BPH e Viardot is therefore the single most useful initial test when either primary hyper- or hypothyroidism is suspected. FT3 measurement can also be useful, especially BPH e Viardot there is an abnormality of growth hormone production growth hormone insufficiency can BPH e Viardot the conversion of FT4 to FT3. While theoretically the plasma level of FT3 can be of value in assessing patients with hypothyroidism, there are many factors that confound interpretation, such as the individual patient set-point which is unknownrecent illness or calorie and iodine intake.
In patients with primary hypothyroidism and in iodine deficiency FT3 levels are generally preserved within population limits until relatively late unlike in hyperthyroidismmaking it an insensitive marker. In patients taking T3 replacement, either alone or in combination with T4 e. As with patients taking conventional replacement treatment, TSH is BPH e Viardot the primary analyte by which to adjust dose. Insulin-like growth factor 1 IGF-1 is an accepted test for the initial investigation of growth hormone excess acromegaly, gigantismand in monitoring the treatment of such patients.
IGF-1 may also be requested, when recommended by a Chemical Pathologist or Endocrinologist, as an initial investigation of the possibility of growth hormone deficiency. However, interpretation is much more likely to be confounded by other factors, such as nutritional status, oestrogen BPH e Viardot thyroid hormone status. A low result is more likely to be clinically significant when prior suspicion is high, e. Formal diagnosis of growth hormone deficiency i. Measurement of IGF-1 in patients on certain weight loss diets, e.
Growth hormone measurement can be helpful in the evaluation of patients with pituitary disease, particularly when acromegaly is suspected or in children or adults when there is suspicion of hypopituitarism.
The test is funded if one of these indications is specified on the request form, or when ordered by an Endocrinologist. A major problem limiting interpretation, however, is that growth hormone is secreted in a pulsatile fashion, so unless a result is clearly high or low, a single isolated result can be impossible to interpret.
Stimulation or suppression tests, or serial measurements throughout the day, provide additional information; this should only be carried out under specialist management or recommendation. Plasma insulin levels are a key measurement when establishing a diagnosis of insulinoma as a cause of recurrent hypoglycaemia; since insulin has a plasma half-life of minutes and insulin secretion is shut off by hypoglycaemia in normal patients, plasma insulin levels should be BPH e Viardot.
As evaluation of possible insulinoma is complex, prior discussion with an Endocrinologist or BPH e Viardot Pathologist is recommended before requesting this test.
Patients who have had bariatric surgery can develop excessive inappropriate pancreatic insulin secretion. For these patients, measuring insulin and glucose together at the time BPH e Viardot describe symptoms is BPH e Viardot reasonable for any referrer, as long as the clinical information details that the patient had previous bariatric surgery. While controversial, the biochemistry subgroup felt that evidence to justify funding of plasma insulin to identify insulin resistance and the metabolic syndrome was not sufficiently robust to justify public funding, except in specialist settings and then preferably when used as part of a calculation incorporating concurrent glucose level.
For example, calculation of the HOMA index of insulin resistance may be useful in assessing the probability of non-alcoholic steatohepatitis NASH and the need for liver biopsy to assess fibrosis. Insulin levels are not useful BPH e Viardot patients with diabetes, as they can range from very high to unmeasurably low.
They should also not be used to decide whether a patient has type 1 or type 2 diabetes; other tests such as diabetes-related antibodies anti-GAD, anti-IA2 and plasma C-peptide have greater utility. C-peptide is BPH e Viardot in secretory granules with insulin and co-released in equimolar amounts.
Measuring plasma C-peptide is useful in the context of evaluating possible excess endogenous insulin secretion e. Fasting status or relationship to meals should be well defined and plasma glucose should be measured concurrently. Ideally the sample should be taken during a spontaneous hypoglycaemic attack or a controlled fast, with careful correlation with symptoms.
C-peptide is filtered by the glomeruli and caution should be exercised in patients with reduced GFR as this may lead to elevated values independent of any changes in pancreatic status.
C-peptide may also be helpful in classifying some patients, when there is uncertainty as to whether they have type 1 or type 2 diabetes. Essential fatty BPH e Viardot EFAs are divided into two main classes: omega-3 and omega The shortest chain omega-3 essential fatty acid is linolenic acid, and the shortest omega-6 is linoleic acid.
There is considerable literature on the biology and benefits of n3 and n6 EFAs, and increased intake of omega-3 rich foods has been reported to have beneficial cardiovascular and anti-thrombotic effects, as well as a wide range of other less well substantiated BPH e Viardot.
EFA testing is technically difficult and very expensive. This test is not appropriate for patients who are considering or taking EFA supplements.
Based on current evidence, knowing the detailed composition of EFAs in plasma and red cells was not considered sufficient to justify publically funding such requests at this time.
Targets to guide treatment are not clearly established, correlation with tissue levels is imperfect, and there is potential for confusion due to the range of other biological and dietary influences. Achieving an BPH e Viardot balance of EFAs is important in some limited clinical settings, such as patients with severe liver disease or short bowel syndrome on intensive nutritional support. An EFA test would be appropriate in this setting. Vitamins B1 thiamineB2 riboflavinand B6 pyridoxine.
Plasma levels of these vitamins are sometimes requested as part of an overall nutritional or wellness screen. All of these vitamins are water soluble with very limited storage in tissues such as fat, hence plasma levels will be very influenced by recent short-term intake. The assays are all expensive and there are significant pre-analytical factors of collection, processing and BPH e Viardot to consider which, if not addressed correctly, will invalidate the result.
Even if the patient is suspected to have a deficiency, testing is BPH e Viardot unhelpful as the turnaround is slow. The clinical response to vitamin supplementation is more helpful in confirming the diagnosis, and is the only way to prove that symptoms leading to the suspected diagnosis were related to deficiency of that particular vitamin.
Post-operative monitoring of nutritional status is considered appropriate in this situation and requests for vitamin B1 and B6 are approved. Vitamin D has a central role in bone and calcium metabolism and vitamin D tests were developed for investigation of abnormalities of calcium metabolism as well as metabolic bone disorders, such as rickets and osteomalacia. In recent years an association has been reported between low vitamin D levels and a very wide range of disorders cancers, cardiovascular disease, diabetes, autoimmune disorders and BPH e Viardot diseases.
However, a causal link has yet to be demonstrated for any of these conditions. Despite this, the BPH e Viardot of requests for vitamin D tests has increased dramatically, with many patients who get reasonable sun exposure and who are otherwise at relatively low risk, wishing to know their vitamin D level. A comprehensive literature review for the Ontario Ministry of Health concluded that there is little evidence that it is useful to test vitamin D concentrations in patients without symptoms of metabolic bone disease.
It is not necessary to routinely measure vitamin D in patients with low bone density.