False positive carbohydrate antigen 19-9 (CA19-9) results due to a low-molecular weight interference in an apparently healthy male.

BACKGROUND: We investigated the presence of interference in a patient who had an elevated CA19-9 concentration using the ADVIA Centaur but results within reference limits with ROCHE Modular Analytics E170 and Brahms KRYPTOR analysers. METHODS: We performed repeat analyses using the same (ADVIA Centaur) and alternate immunossays (Roche Modular Analytics E170 and Brahms KRYPTOR) on the patient's sample and investigated for known interferences. To determine the nature of the interference, we measured CA19-9 on the ADVIA Centaur after dilution experiments and after incubation with non-immune animal sera and in heterophilic blocking tubes (HBT). We also undertook polyethylene glycol precipitation, lectin inhibition experiments and gel filtration chromatography. RESULTS: A curvilinear response to dilution was observed with the ADVIA Centaur. Other known interferences were excluded. Treatment with HBT or non-immune animal sera did not give clinically different results from untreated samples. There was only 0.59% recovery after PEG precipitation in the sample from the case patient. Lectin reduced the assay signal in four patient samples (recovery=1.9-14.1%) but not in the case patient (recovery=106.2%). Gel filtration studies suggested the presence of a low molecular weight (approximately 100 kDa) interference in the case patient's serum. CONCLUSIONS: We report a novel mode of interference and show a non-CA19-9, low molecular-weight interference affecting the ADVIA Centaur CA19-9 immunoassay.

A review of eGFR reporting after 6 months in practice.

BACKGROUND: Following the introduction of routine calculation of estimated glomerular filtration rate (eGFR) from all serum creatinine values in samples received from general practice it was noted that there was a preponderance of values consistent with chronic kidney disease (CKD) stage 3 or higher. METHODS: A review was conducted of all eGFR values from 51 314 individuals received from primary care during October 2006 to April 2007. RESULTS: It was found that more than 25% of eGFR results indicated CKD stage 3 or higher. The median age in this group was 64 years (range 18-104 years) while that of the local general population according to the 2001 census was 40 years (range 18-104 years); these ages were statistically significantly different (p<0.001). There was no difference between the groups with regard to gender. The eGFR data were therefore corrected for age distribution, and an estimated prevalence of 5.6% of eGFR consistent with CKD stage 3 was found. This was a higher proportion than estimates of CKD suggested before the introduction of eGFR. CONCLUSIONS: The higher proportion of CKD stage 3 may be due to difference in age and gender in populations studied, as there is a marked effect of age on calculated eGFR values found.

Helicobacter pylori infection potentiates the inhibition of gastric acid secretion by omeprazole.

BACKGROUND: Omeprazole has a greater intragastric pH elevating effect in Helicobacter pylori positive than negative subjects. Ammonia production by H pylori has been suggested as a probable mechanism. AIMS: To assess the effect of H pylori status on gastric acid secretion during omeprazole treatment, and to examine the possible role of ammonia neutralisation of intragastric acid in increased omeprazole efficacy in infected subjects. METHODS: Twenty H pylori positive and 12 H pylori negative healthy volunteers were examined before and six to eight weeks after commencing omeprazole 40 mg/day. On both occasions plasma gastrin and acid output were measured basally and in response to increasing doses of gastrin 17 (G-17). Gastric juice ammonium concentrations were also measured. RESULTS: Prior to omeprazole, measurements were similar in the H pylori positive and negative subjects. During omeprazole, median basal intragastric pH was higher in the H pylori positive (7.95) versus negative (3.75) subjects (p<0.002). During omeprazole basal, submaximal (180 pmol/kg/h G-17), and maximal acid outputs (800 pmol/kg/h G-17) were lower in H pylori positive subjects (0.0, 3.6, 6.0 mmol/h respectively) versus negative subjects (0.3, 14.2, 18.6 mmol/h) (p<0.03 for each). This effect was not explained by neutralisation by ammonia. CONCLUSION: The presence of H pylori infection leads to a more profound suppression of acid secretion during omeprazole treatment. The effect cannot be explained by neutralisation of intragastric acid by bacterial ammonia production and its precise mechanism has to be explained.

Incorrect diagnosis of diabetes mellitus in a patient with persistence of fetal haemoglobin.

A 65-year-old woman, referred to the endocrine clinic for investigation of tiredness and arthritis, was diagnosed as having diabetes on the basis of a positive family history and a raised glycated haemoglobin (HbA1) measurement. Subsequently, she was shown not to have diabetes but to have a persistently raised haemoglobin F (HbF) level. Initial assessment of HbF level by electroendosmosis demonstrated a normal HbF level but high values were confirmed using HPLC. Thalassaemia was excluded following DNA analysis. This case illustrates the importance of a glucose tolerance test following WHO criteria for the diagnosis of diabetes and emphasises that HbA1 is not a diagnostic test for diabetes.

Helicobacter pylori does not release cysteamine into gastric juice.

AIM: To determine whether Helicobacter pylori releases cysteamine into gastric juice as cysteamine is known to be ulcerogenic. METHODS: Samples of fasting gastric juice were collected from 22 individuals (four women); 10 subjects were H pylori negative. The presence of infection was confirmed by examination and culture of gastric biopsies. Cysteamine in gastric juice was measured by reversed phase gradient high performance liquid chromatography with a detection limit of 10 mumol/l. RESULTS: Cysteamine was not detected in any of the gastric juice samples or in extracts of cultured H pylori. CONCLUSIONS: If H pylori produces cysteamine then the amounts produced are insignificant and are unlikely to explain the association between H pylori infection and the development of duodenal ulcer disease.

Timed sequential analysis of creatine kinase in the diagnosis of myocardial infarction in patients over 65 years of age.

AIM: To assess the value of timed sequential analysis of creatine kinase (CK) activity for the early diagnosis of acute myocardial infarction (AMI) in patients over 65 years of age. METHOD: Samples were collected on admission and eight to 12 hours later from 156 patients over 65 years of age. Routine cardiac enzyme activities were determined and serial electrocardiograms (ECGs) recorded. The predictive value of timed samples for CK activity, standard cardiac enzyme activities, and ECGs was compared with the final diagnosis on discharge. RESULTS: Forty one patients had a discharge diagnosis of AMI, 83 of angina pectoris, and the remaining 32 patients had other diagnoses. Electrocardiograms had a sensitivity of 55% and a specificity of 96%, giving a predictive value of 86% for a negative and 84% for a positive ECG. Standard cardiac enzymes had a predictive value of 99% for a negative result but only 68% for a positive result. The logarithm of the rate of change of CK activity had a predictive value of 97% for a negative result and 95% for a positive result. CONCLUSION: This study has shown that slope analysis of CK activity can be used for the early diagnosis of AMI in patients over 65 years of age, and that this was not affected by the presence of possible confounding diagnoses.

Creatine kinase isoform electrophoresis for the early confirmation of myocardial infarction detected by timed sequential CK slope analysis.

Creatine kinase (CK)-MM and -MB isoforms were evaluated for the early diagnosis of myocardial infarction in patients aged over 65 years admitted to a district general hospital with acute chest pain. Samples were collected for standard cardiac enzymes, timed CK slope analysis, and CKMM and CKMB isoform analysis from 48 patients admitted with acute chest pain. CKMM and CKMB isoform analyses were conducted using a Helena Rep electrophoresis system under standard conditions supplied by the company. In addition to the results of the biochemical tests the discharge diagnosis of the patients were also recorded. CKMM isoform analysis resulted in three false-negative classifications of patients and one false-positive. The predictive value of this test was 100% for a positive result and 94% for a negative result. CKMB isoform analysis was less accurate and there were six false-negative results and five false-positive results. The predictive value of a positive result was 75% and 85% for a negative result. CK isoform analysis became unreliable when mean total CK levels in serum were 210 IU/l (+/- 171). CK isoform analysis may be of use in the investigation of patients whose samples have a total CK concentration greater than the reference range but was no better than timed CK slope analysis for the detection of myocardial infarction in patients aged more than 65 years.

Urease-mediated destruction of bacteria is specific for Helicobacter urease and results in total cellular disruption.

The survival of Helicobacter mustelae, Proteus mirobilis, Escherichia coli and Campylobacter jejuni in the presence of urea and citrate at pH 6.0 was examined. H. mustelae, which has urease activity similar to H. pylori, had a markedly reduced survival, median 2.5% (0-78%) (P < 0.001) when incubated under these conditions. Only 7% of the ammonia produced by H. mustelae urease activity was recovered from the buffer, a similar percentage to that previously reported with H. pylori. None of the other organisms, all of which had lower urease activity, had impaired survival under these conditions. Electron microscopical studies demonstrated extensive structural damage to H. pylori following exposure to urea and citrate at pH 6.0. This structural damage to the organisms makes it unlikely that the low recovery of ammonia was due to retention of ammonia within the bacteria and suggests that the ammonia may have been incorporated into glutamate or other amino acids. Incorporation of ammonia into these compounds would deplete the cell of the key metabolic intermediate alpha-ketoglutarate and could thus explain the mechanism of the urease-dependent destruction of the organism.

Cholesterol and lipoprotein(a) as risk factors for coronary heart disease in elderly subjects.

The changes in lipoprotein(a) concentration that occur with age as a result of its association with an increased risk of coronary artery disease were investigated. Lipoprotein(a) concentrations were measured in serum samples from healthy volunteers, individuals with premature coronary artery disease, individuals with hyperlipidaemia but without evidence of premature coronary artery disease, and also in elderly men and women who had hyperlipidaemia. Concentrations in individuals with premature coronary artery disease were the same as those of the healthy volunteers, while in both these groups they were lower than those found in hyperlipidaemic elderly men and women, and those found in hyperlipidaemic women aged 36-68 years. No association between raised lipoprotein(a) concentration and mortality as a result of premature coronary artery disease was demonstrated. Raised lipoprotein(a) levels found in the hyperlipidaemic individuals also suggested that it may not be an independent risk factor.

Making the new deal for junior doctors happen.

How can the new deal for juniors be implemented in today's overstretched health service? How do you get clinicians and management to work together? On the Wirral falling house officer morale and recruitment stimulated a new approach, action learning, which proved to be highly successful. Action learning is not a new approach in management terms, but it is rarely used in the health service. Guided by an experienced facilitator, a group of people learn management skills by exploring and resolving practical problems relevant to them. A group of general practitioners and consultants used action learning to teach themselves more about management and at the same time to make changes which addressed many of the junior doctors' difficulties and solved the hospital recruiting problem.

On-call duties in chemical pathology: a survey of junior medical staff in the UK.

To ascertain the extent of variation in out-of-hours duties among trainees in chemical pathology in the UK questionnaires were sent to 81 junior medical staff in 1992. Replies were received from 63 (78%). Although most had participated in an advisory rota, only 41 (65%) had participated in an analytical rota. Nine (14%) had participated in specialist analytical rotas, while 13 (21%) had experience of multidisciplinary rotas and only eight (13%) had experience of rotas involving clinical responsibility. Only 10 (16%) regularly reviewed their work on call with their senior medical staff. There was no single method of requesting tests out of hours in the trainees' laboratories and there was also considerable variation with respect to the tests available out of hours. It is concluded that sufficient variation exists in the on-call experience gained by junior medical staff in chemical pathology to raise concern about the quality of training in out-of-hours work.

Effect of Helicobacter pylori infection on intragastric urea and ammonium concentrations in patients with chronic renal failure.

AIM: To assess the value of measuring the gastric juice urea:ammonium ratio in detecting Helicobacter pylori infection in patients with chronic renal failure. METHODS: Twenty three (12 men) patients with established chronic renal failure and dyspepsia were studied. Gastric juice (2 ml) was aspirated during endoscopy to measure urea and ammonium. The upper gastrointestinal tract was routinely inspected and two antral biopsy specimens obtained. The 14C-urea breath test was conducted within 14 days of endoscopic examination to determine H pylori antibody response. RESULTS: The median (range) serum urea concentration in 11 patients with renal failure and H pylori infection was similar to that in 12 without H pylori infection. The median gastric juice urea concentration in subjects with infection was lower than that in the subjects without infection (p < 0.01). The median gastric juice ammonium concentration in subjects with the infection was higher compared with subjects without infection (p < 0.01). There was an overlap of the urea and ammonium concentrations in gastric juice from both H pylori positive and negative subjects. The urea:ammonium ratio was 0.16 (0.01-1.11) for subjects with H pylori compared with 1.63 (1.0-18.9) in subjects without infection (p < 0.001). CONCLUSION: The urea:ammonium ratio differentiated both groups, with the exception of one false negative result. The urea:ammonium ratio proved almost as effective in identifying the presence of H pylori infection in subjects with chronic renal failure as it had in subjects with normal renal function.

Use of multichannel discrete analyser to reduce unnecessary biochemical tests.

AIM: To investigate the waste of laboratory reagents which resulted from the process of ordering biochemistry profiles. METHODS: The frequency of measurement of 15 analytes was recorded during the six months before the introduction of a system of discretionary requesting and analysis of samples (high capacity multichannel discrete analyser), and also during the same six month period one year and two years after its introduction. RESULTS: The frequency of measurement of 10 of the 15 analytes decreased during the six month period one year after the change to discretionary testing. The remaining five analytes were measured up to 22% more frequently. There was an overall decrease in the measurement of biochemical tests by 31,359. This created an annual cost saving of 7124 pounds. In the second year five analytes still continued to be measured less frequently than originally but the remaining 10 analytes were measured more frequently. This resulted in an overall increase in the measurement of biochemical tests by 53,678 compared with the six month period before discretionary analysis. The pattern of requests was similar during both periods of discretionary requesting studied and as a result, a small annual cost saving of 1672 pounds was again made. CONCLUSION: Discretionary requesting and analysis of tests may eliminate the measurement of clinically unnecessary test which had previously resulted from the processes of ordering tests. These cost savings may be rapidly eroded by an increase in the laboratory workload.

Measurement of urea and ammonium concentrations in gastric juice.

AIM: To study the effect of known interference in the measurement of urea and ammonium concentrations in samples of gastric juice. METHODS: The effect of pH and ammonium concentration on the o-pthalaldehyde method, the diacetylmonoxime method, a Berthelot linked method and an enzymatic urease method for the measurement of urea in gastric juice was therefore conducted. An enzymatic method of the measurement of ammonium in gastric juice was also assessed. RESULTS: The o-pthalaldehyde and the enzymatic urease methods were unaffected by a low gastric juice pH, ammonium concentrations of 10 mmol/l, and had interassay coefficients of variation of 3.9-5.6% and 2.8-10.6%, respectively, over a urea concentration of 2.5 mmol/l-20 mmol/l. The Berthelot linked method resulted in low gastric juice urea concentrations. The enzymatic method of ammonium measurement also proved suitable when the effect of low gastric juice pH was controlled. CONCLUSION: Interference by low pH did not explain the differences in reports of gastric juice urea or ammonium concentrations.