ARCHITECT Forum
Xchange newsletter - Autumn 2007
As we reported in Xchange 21, June’s ARCHITECT Forum was an extremely popular event. Day two focussed on the latest scientific and technical hot topics in biochemistry, immunoassay and infectious diseases. Featured here are some highlights from the forum.
‘Abbott HIL Indices: Interference Assessment for Haemoglobin, Icterus, and Lipaemia (HIL)’
Kelley Carville, Abbott Diagnostics
Test result accuracy is dependent on specimen integrity. Interferents that can impact test results include:
- Haemoglobin derived from haemolysis
- Bilirubin (Icterus) from hepatic or haemolytic disease
- Lipaemia due primarily to elevated triglycerides
It was shown that approximately half the delegates at the meeting currently performed HIL testing and, of those, half ran all three indices.
‘Using Serum Indices – The Glasgow Experience’
John Allison, Southern General Hospital, Glasgow
John Allison reported that all three HIL indices are measured at Southern General Hospital with cut-off levels set at those concentrations giving less than 10% interference. They found the benefits of using indices included:
- Interference results were standardised across Glasgow
- Took the objectivity out of what represented a haemolysed or lipaemic sample
- Allowed the reflex testing of enzymatic creatinine to be an automatic process
However, other factors had to be considered: If using saline, measurement of serum indices required an extra pipetting step per sample and a reagent space on the carousel was necessary.
‘Lipaemia and its Interference Effects Upon Abbott AEROSET/ARCHITECT Assays’
Stuart Pople, University Hospital Wales, Cardiff
Stuart Pople described a study performed by his laboratory looking at the effect of lipaemia on measurement of different analytes. Samples were divided and one portion loaded directly onto an analyser. The second portion was ultracentrifuged and only the infranatant was analysed.
‘Total Allowable Error’, TEa, was used as defined by CLIA-88 (Clinical Laboratories Improvements Amendments). This takes into consideration factors such as analytical imprecision and medical decision intervals. Results of the Cardiff study can be found in table 1.
Assays demonstrating no significant interference1 |
Analytes demonstrating significant lipaemia interference |
L-index (>TEa) |
Direction |
| Potassium; Bicarbonate; Urea; Creatinine; Calcium; Albumin (BCG); CRP; AST; ALP; GGT; CK; Amylase; LDH; Direct Bilirubin | Sodium | 30 | Negative |
| Chlorine | 50 | Negative | |
| Glucose | 70 | Negative | |
| Phosphate | 10 endo, 25 TPN | Negative | |
| Total Bilirubin | ? Variable | Slightly negative | |
| Magnesium | 20 | Positive | |
| ALT | 15 | Positive | |
| Total Protein | 10 | Positive | |
| Uric Acid | 10 endo | Positive |
Table 1
1 Where paired results fall within TEa, at lipaemia levels up to 100 on the L-index
‘Diagnostic Steps in Addison’s and Cushing’s and the Role of Steroid Measurements’
Prof Wiebke Arlt, University of Birmingham
When describing the various clinical disease states associated with adrenal function disorders, Prof Arlt highlighted the importance of using biochemical tests to support diagnosis and treatment of patients.
Addison’s Disease is caused by low cortisol levels and may be termed as hypocortisolism or adrenal insufficiency. Prof Arlt looked at tests used to diagnose the condition, including two dynamic tests commonly used for hypothalamic-pituitary-adrenal (HPA) axis assessment: the insulin tolerance test (ITT) and the high-dose short synacthen stimulation test (SST).
The ITT is regarded as the ‘gold standard’ but has limitations as it is expensive, unpleasant for the patient and requires medical supervision. The high-dose SST on the other hand is less expensive, simple and safe, but concern remains that it can give rise to falsely reassuring results. Prof Arlt reviewed a number of studies which showed that, for clinical decision making, the high dose SST is a suitable and reliable alternative to the ITT in the assessment of the HPA axis.
For further information on any of these presentations, contact your local Abbott representative.