The impact of change in albumin assay on reference intervals, prevalence of 'hypoalbuminaemia' and albumin prescriptions.

BACKGROUND: We studied the impact on reference intervals, classification of patients with hypoalbuminaemia and albumin infusion prescriptions on changing from a bromocresol green (BCG) to a bromocresol purple (BCP) serum albumin assay. METHODS: Passing-Bablok regression analysis and Bland-Altman plot were used to compare Abbott BCP and Roche BCG methods. Linear regression analysis was used to compare in-house and an external laboratory Abbott BCP serum albumin results. Reference intervals for Abbott BCP serum albumin were derived in two different laboratories using pathology data from adult patients in primary care. Prescriptions for 20% albumin infusions were compared one year before and one year after changing the albumin method. RESULTS: Abbott BCP assay had a negative bias of approximately 6 g/L compared with Roche BCG method.There was good agreement (y = 1.04 x - 1.03; R(2 )= 0.9933) between in-house and external laboratory Abbott BCP results. Reference intervals for the serum albumin Abbott BCP assay were 31-45 g/L, different to those recommended by Pathology Harmony and the manufacturers (35-50 g/L). Following the change in method there was a large increase in the number of patients classified as hypoalbuminaemic using Pathology Harmony references intervals (32%) but not when retrospectively compared to locally derived reference intervals (16%) compared with the previous year (12%). The method change was associated with a 44.6% increase in albumin prescriptions. This equated to an annual increase in expenditure of £35,234. CONCLUSIONS: We suggest that serum albumin reference intervals be method specific to prevent misclassification of albumin status in patients. Change in albumin methodology may have significant impact on hospital resources.

Investigation of a problem with external quality assurance samples for faecal occult blood.

BACKGROUND: It is vital that laboratories participate in External Quality Assurance (EQA) programmes, but results from such schemes do not necessarily help ensure assays are 'in control'. We describe a series of experiments undertaken to explore apparent poor performance in an occult blood EQA scheme that manifested as a series of false-negatives. As a consequence of our laboratory misclassifying some EQA samples, we decided to design a simple sensitivity study that would reaffirm confidence in our testing procedures. METHODS: In order to verify analyst reliability and analytical sensitivity, a series of 10 faecal samples were supplemented with increasing amounts of whole blood (0-1.0 mg/Hb/g faeces) and these were then tested independently by four different operatives. EQA samples which our laboratory misclassified were shared with and tested by a second laboratory and results compared. RESULTS: The results demonstrated consistency in interpretation among the four 'testers' and also suggested that the sensitivity of the method is 0.7 rather than 0.6 mg/Hb/g faeces as claimed by the manufacturer. The second laboratory obtained identical results as our laboratory for the EQA samples which our laboratory had misclassified. CONCLUSIONS: Occult blood EQA scheme results might not give a true reflection of a laboratory's ability to provide reliable results. We would encourage any laboratory observing relative poor performance to undertake local sensitivity studies and repeat testing of EQA samples if in any doubt.

Are biochemistry interpretative comments helpful? Results of a general practitioner and nurse practitioner survey.

BACKGROUND: Adding or incorporating clinical interpretative comments on biochemistry results is widespread in UK laboratories; although this consumes considerable human resource, there is still little evidence to suggest that it is either effective or appreciated by our clinical colleagues. I therefore decided to survey our local general practitioners (GPs) and nurse practitioners to analyse whether they found biochemistry comments on reports helpful. METHODS: A simple questionnaire was designed and sent to 159 GPs and 81 nurse practitioners asking them whether they found this activity useful for the limited range of test groups that we routinely comment on and also whether they would like to see commenting on more groups of tests. RESULTS: Overall, 49.6% of questionnaires were returned. Of these, there was overwhelming support for commenting on reports and 77% would like to see comments on a greater range of tests. CONCLUSIONS: Although adding clinical interpretative comments is very time-consuming for senior laboratory staff, there is overwhelming support of this activity among our GPs and nurse practitioner users; therefore, our local policy of routinely adding clinical comments will remain for the foreseeable future.