Basingstoke and north hampshire hospital pathology user handbook

Patient preparation
Gender, age, diet, time of day, exercise, posture and prolonged venous occlusion are all factors that may influence some investigations. If in doubt, ask.

Many drugs can interfere with tests. If in doubt, state which drugs your patient is taking. Further information on factors affecting individual tests may be found in the Test Index.

Samples
See also 'Phlebotomy'
Please give time of sample collection (especially important if urgent or in case of blood glucose, cortisol, dynamic function tests, therapeutic drugs etc.).
Please avoid delays in getting the blood samples to the laboratory. Some special samples have to be separated within 10 minutes of collection, as they are unstable. Do not refrigerate unseparated specimens.
Blood specimen tubes
Please refer to the test index for the full list of sample requirements. In general:
1. Clotted blood is preferred for the majority of biochemistry investigations (gold topped vacuum tube) and is essential for lithium analysis.
2. Fluoride-oxalate blood is needed for glucose or lactate (grey top vacuum tube). Within the hospital, clotted blood is accepted for glucose except for glucose tolerance tests. Outlying sites must use grey top tubes.

3. 
   EDTA blood is needed for HbA1c, ammonia, renin/aldosterone, ACTH and carbon monoxide (lavender top vacuum tube).
   

3. 
   For most combinations of tests, 4ml of clotted blood (gold top) will suffice.
   

Paediatric samples
Special tubes are available for paediatric use. Heparinised blood is acceptable for most tests as it yields more plasma from very small samples than clotted blood. Where applicable, please clearly indicate order of priority among tests when several are requested on samples of small volume

(e.g. 1-Na/K; 2-Creatinine; 3-LFT).

Blood samples that must be taken in the phlebotomy suite at BNHFT

or from in-patients at BNHFT and brought immediately to pathology reception:

ACTH Aldosterone/Renin

Ammonia Calcitonin

Carboxy/Met haemoglobin C Peptide

Cryoglobulin Cyclosporin

G-1-P UT Growth Hormone Gut hormones Hydroxybutyrate

IGF1 Insulin (Glucose at the same time) Lead/heavy metals Methotrexate PTH (Calcium at the same time) Porphyrins Renin/Aldosterone Retinol binding Protein Tacrolimus, Everolimus, Serolimus Tryptase Vitamins D 17 Hydroxyprogesterone
Special tests and Dynamic Function Tests

The above tests require special collection procedures. There are protocol sheets available from the laboratory for tests, some additional to those above, which may involve special patient preparation and/or the injection of hormones and serial specimen collections. Please contact the laboratory before taking a sample. The list is not exhaustive - if in doubt, ask

Thyroid Function Testing

For the routine assessment of thyroid function only TSH is performed as the first line test. Free T3 and/or free T4 will only be performed by the laboratory if the TSH concentration is outside the reference range or if specifically requested by the requesting clinician. It is therefore important that the requesting clinician specifically requests free T3 on all patients who are receiving or who have received treatment for thyrotoxicosis. Similarly, free T4 should always be specifically requested on patients with known or possible hypothalamic pituitary disease.

Lithium

Lithium has a narrow therapeutic range necessitating blood levels between 0.4 – 1.2 mmol/L. The lower end of this range is used for elderly and infirm patients and the upper end for younger patients, particularly those being treated for an episode of mania. It is entirely possible for an elderly patient at the upper limit to experience toxicity. The NICE guidance is that when initiating long-term treatment, clinicians should aim for levels of 0.6 – 0.8 mmol/L, with higher levels possibly being of benefit for patients with predominantly manic symptoms.

Antibiotic levels – Gentamicin and Vancomycin

Use Chemical Pathology request protocol. Requests out of hours will be referred to the Consultant Microbiologist on call.

Fluids

Pleural, ascitic or drain fluids should be sent in a white top universal container.

Calculi

Calculi should be sent in a white top universal container.

Please do not use boric acid (red top) containers as the stone fragments may be difficult to locate amongst the boric acid crystals.

Faeces

Faecal samples should be sent in a plain wide-mouthed lab container. The minimum of a grape-sized sample is required but do not fill the container more than two-thirds full.

Urine samples

Bottles for 24 hour urine collections are issued by the laboratory together with an instruction sheet relevant to the test requested. The following are best performed on 24-hour collections:

Electrolytes Uric Acid Cortisol

Creatinine clearance^* Catecholamines/metabolites^** Calcium^*** Phosphate^*** Oxalate^*** Citrate^***

* Ensure 5 ml of clotted blood is collected within the 24 hours of the urine collection. This should be sent to the laboratory attached to the urine container. Outpatients should bring their 24 hour urine sample to the laboratory on the morning of final collection and have blood taken from them before they leave the laboratory.
** Catecholamines/metabolites and 5HIAA should be collected into acetic acid.

Special container available from laboratory as is a list of interfering drugs.

*** Calcium, Phosphate, Citrate, Oxalate must be collected into hydrochloric acid.

Special container available from laboratory, CARE required.

Protein/creatinine ratios are a useful screen in place of 24 hour protein output and can give a rapid result in conditions such as pre-eclampsia.

Most of these tests can also be performed on spot samples for paediatric patients when the ratio to creatinine will be reported.

All other commonly requested urine investigations require random urine samples. A plain 'universal' container is required (white top), not one containing boric acid (red top).