A worldwide multicentre comparison of assays for cerebrospinal fluid biomarkers in Alzheimer's disease.

BACKGROUND: Different cerebrospinal fluid (CSF) amyloid-beta 1-42 (Abeta(1-42)), total Tau (Tau) and Tau phosphorylated at threonine 181 (P-Tau) levels are reported, but currently there is a lack of quality control programmes. The aim of this study was to compare the measurements of these CSF biomarkers, between and within centres. METHODS: Three CSF-pool samples were distributed to 13 laboratories in 2004 and the same samples were again distributed to 18 laboratories in 2008. In 2004 six laboratories measured Abeta(1-42), Tau and P-Tau and seven laboratories measured one or two of these marker(s) by enzyme-linked immunosorbent assays (ELISAs). In 2008, 12 laboratories measured all three markers, three laboratories measured one or two marker(s) by ELISAs and three laboratories measured the markers by Luminex. RESULTS: In 2004, the ELISA intercentre coefficients of variance (interCV) were 31%, 21% and 13% for Abeta(1-42), Tau and P-Tau, respectively. These were 37%, 16% and 15%, respectively, in 2008. When we restricted the analysis to the Innotest (N = 13) for Abeta(1-42), lower interCV were calculated (22%). The centres that participated in both years (N = 9) showed interCVs of 21%, 15% and 9% and intra-centre coefficients (intraCV) of variance of 25%,18% and 7% in 2008. CONCLUSIONS: The highest variability was found for Abeta(1-42). The variabilities for Tau and P-Tau were lower in both years. The centres that participated in both years showed a high intraCV comparable to their interCV, indicating that there is not only a high variation between but also within centres. Besides a uniform standardization of (pre)analytical procedures, the same assay should be used to decrease the inter/intracentre variation.

White matter lesion severity is associated with reduced cognitive performances in patients with normal CSF Abeta42 levels.

OBJECTIVE: To identify possible associations between white matter lesions (WML) and cognition in patients with memory complaints, stratified in groups with normal and low cerebrospinal fluid (CSF) Abeta42 values. MATERIAL AND METHODS: 215 consecutive patients with subjective memory complaints were retrospectively included. Patients were stratified into two groups with normal (n = 127) or low (n = 88) CSF Abeta42 levels (cut-off is 450 ng/l). Cognitive scores from the Mini-Mental State Examination (MMSE) and the Neurobehavioral Cognitive Status Examination (Cognistat) were used as continuous dependent variables in linear regression. WML load was used as a continuous independent variable and was scored with a visual rating scale. The regression model was corrected for possible confounding factors. RESULTS: WML were significantly associated with MMSE and all Cognistat subscores except language (repetition and naming) and attention in patients with normal CSF Abeta42 levels. No significant associations were observed in patients with low CSF Abeta42. CONCLUSIONS: WML were associated with affection of multiple cognitive domains, including delayed recall and executive functions, in patients with normal CSF Abeta42 levels. The lack of such associations for patients with low CSF Abeta42 (i.e. with evidence for amyloid deposition), suggests that amyloid pathology may obscure cognitive effects of WML.

Prostatic acid phosphatase, purification and iodination using Iodogen.

Prostatic acid phosphatase was purified from prostatic adenomas. The procedure involved chromatography on Concanavalin A-Sepharose, DEAE-cellulose, Bio-Gel P-150 and L-tartrate-Sepharose. The purified phosphatase hydrolyzed p-nitrophenyl phosphate at a rate of 270 mumol . mg-1 . min-1 (25 degrees C) and showed homogeneity upon polyacrylamide gel electrophoresis in sodium dodecyl sulfate. The final prostatic acid phosphatase preparation was pure and the antisera were monospecific as judged by the highly sensitive technique of crossed immunoelectrophoresis. Of the procedures evaluated for the iodination of the purified enzyme, oxidation with Iodogen was found to give the best iodinated product.

Increased cerebrospinal fluid levels of nerve cell biomarkers in narcolepsy with cataplexy.

BACKGROUND: The association between narcolepsy with cataplexy and the hypocretinergic system in the central nervous system is strong since up to 75-90% of all patients have cerebrospinal fluid (CSF) hypocretin-1 deficiency. The predominant occurrence of HLADQB1*0602 tissue type in narcolepsy patients and recent results from genome-wide association studies suggest an underlying immunological mechanism. The present study was initiated to clarify whether measurement of nerve cell biomarkers in CSF could give additional knowledge of the pathophysiological mechanisms causing narcolepsy with cataplexy. METHODS: Two patient groups with narcolepsy, comprising 18 patients with low CSF hypocretin-1 concentrations and typical cataplexy, and 18 patients with normal CSF hypocretin-1 levels and mild cataplexy-like symptoms, were compared to 17 controls. We measured the nerve cell biomarkers beta-amyloid (Aß42), total tau protein (T-tau), phosphorylated tau (P-tau) and neuron-specific enolase (NSE) in CSF. RESULTS: The concentrations of all biomarkers were significantly elevated in both patient groups compared to the controls. The concentration of beta-amyloid was significantly higher in the patient group with normal CSF hypocretin-1 concentration than in those with low concentrations, whereas the other biomarkers showed no difference between the patient groups. CONCLUSION: The findings of elevated levels of CSF biomarkers independent of CSF hypocretin-1 reduction may reflect alterations in cell metabolism. The results suggest a more extensive affection of the sleep regulating cellular network, affecting other neuronal sites important in the regulation of sleep, in addition to the hypocretin-producing neurons.

Morphometric changes in the episodic memory network and tau pathologic features correlate with memory performance in patients with mild cognitive impairment.

BACKGROUND AND PURPOSE: Mild cognitive impairment (MCI) may affect several cognitive domains, including attention and reasoning, but is often first characterized by memory deficits. The purpose of this study was to ask these 2 questions: 1) Can levels of CSF tau proteins and amyloid beta 42 peptide explain thinning of the cerebral cortex in patients with MCI? 2) How are brain morphometry, CSF biomarkers, and apolipoprotein E (APOE) allelic variation related to episodic memory function in MCI? MATERIALS AND METHODS: Hippocampal volume and cortical thickness were estimated by MR imaging and compared for patients with MCI (n = 18) and healthy controls (n = 18). In addition, regions of interest (ROIs) were selected in areas where the MCI group had atrophy and which overlapped with the episodic memory network (temporal, entorhinal, inferior parietal, precuneus/posterior cingulate, and frontal). Relationships among morphometry, CSF biomarkers, APOE, and memory were tested. The analyses were repeated with an independent sample of patients with MCI (n = 19). RESULTS: Patients with MCI and pathologic CSF values had hippocampal atrophy. However, both patients with pathologic and patients with nonpathologic CSF had a thinner cortex outside the hippocampal area. CSF pathology was related to hippocampal volume, whereas relationships with cortical thickness were found mainly in one of the samples. Morphometry correlated robustly with memory performance across MCI samples, whereas less stable results were found for tau protein. CONCLUSION: The differences in hippocampal volume between the MCI and the healthy control groups were only found in patients with pathologic CSF biomarkers, whereas differences in cortical thickness were also found for patients without such pathologic features. Morphometry in areas in the episodic memory network was robustly correlated with memory performance. It is speculated that atrophy in these areas may be associated with the memory problems seen in MCI.

Associations between white matter lesions, cerebrovascular risk factors, and low CSF Abeta42.

OBJECTIVE: To analyze a putative relationship between white matter lesions (WMLs), risk factors for WMLs, and Alzheimer disease (AD) as measured with the surrogate marker CSF Abeta42. METHODS: The authors analyzed effects of acquired risk factors for cerebrovascular disease and WMLs on AD as measured with an intermediate marker, CSF Abeta42. A total of 127 consecutive patients with subjective memory impairment (mean age 66 years; 57 women) investigated at a university-based memory clinic had brain MRI scans. WMLs were rated on a 12-point scale with a semiquantitative procedure. They used path analysis with established and possible risk factors for WMLs and for reduced CSF Abeta42 (age, hypertension, hyperhomocysteinemia, hypercholesterolemia, APOE-epsilon4) as variables. RESULTS: The WML score was 1.5 points higher (p < 0.05) in hypertensive than in nonhypertensive patients and 1.9 points higher (p < 0.05) in patients with hyperhomocysteinemia than in those with normal homocysteine levels. Hypercholesterolemia increased the probability of low CSF Abeta42 levels by 0.2 (p < 0.05). For each point increase in WML score, the probability of low CSF Abeta42 levels increased by 0.03 (p < 0.05). APOE-epsilon4 was associated with reduced CSF Abeta42 (p < 0.01). CONCLUSION: Both hypercholesterolemia and white matter lesions may contribute to low CSF Abeta42 by independent mechanisms.

Acid phosphatases of the human placenta, characterization and immunological comparison with prostatic acid phosphatase.

Four different acid phosphatases, denoted A1, A2, B and C, were separated from human placental homogenates. The enzymes A1, A2 and B were separated from enzyme C by binding to concanavalin A-Sepharose. Although the A1, A2 and B enzymes were all strongly inhibited by L-tartrate, only the A1 enzyme bound by affinity chromatography to L-tartrate-Sepharose. The A2 and B enzymes were separated on DEAE-cellulose. A1, A2 and B had molecular weights about 95,000. Enzyme B had high KM, whereas enzymes A1 and A2 had low KM. The enzymes A1 and A2 bound to antibodies raised against prostatic acid phosphatase, whereas the enzymes B and C did not.

Serum ferritin and transferrin saturation in patients with chronic alcoholic and non-alcoholic liver diseases.

OBJECTIVES: To compare serum ferritin concentration and transferrin saturation in patients with alcoholic and non-alcoholic chronic liver diseases. DESIGN: Consecutive patients with liver diseases. SETTING: The department of internal medicine in a teaching hospital. SUBJECTS: Three hundred and twelve patients with different liver diseases consecutively admitted between 1987 and 1992. INTERVENTIONS: None. MAIN OUTCOME MEASURES: Fasting serum iron, transferrin and ferritin. RESULTS: Serum ferritin was increased above 200 micrograms L-1 in all 18 patients with haemochromatosis (range 310-6500 micrograms L-1), in 64 of 111 alcoholics (58%) and in 30 of 137 (22%) with chronic non-alcoholic liver diseases (P < 0.01). Twelve of 111 alcoholics (11%) had serum ferritin above 1000 micrograms L-1 compared with one of 137 (0.7%) with chronic non-alcoholic liver diseases. In 13 alcoholics who abstained after admission, serum ferritin decreased from 1483 micrograms L1 +/- 1134 to 388 micrograms L-1 +/- 237 (P < 0.001) after 1 1/2 to 6 weeks. The transferrin saturation was increased above 62% in 13 of 18 patients (72%) with haemochromatosis, in 16 of 105 alcoholics (15.2%) and in three of 132 (2.3%) with chronic non-alcoholic liver disease (P < 0.01). CONCLUSION: Serum ferritin is more frequently elevated in abusing patients with alcoholic liver disease than in patients with other chronic liver diseases such as autoimmune liver diseases and hepatitis C. Because serum ferritin decreases rapidly during abstinence, the measurement of ferritin for the detection of haemochromatosis in patients abusing alcohol should be postponed until the patients are abstaining. Most of the patients with increased serum ferritin have normal transferrin saturation values which can be used to separate them from haemochromatosis.

Prostatic acid phosphatase in serum and bone marrow in patients with prostatic carcinoma.

Sixty-two per cent of 61 patients with prostatic carcinoma showed elevated levels of serum acid phosphatase, analysed by radioimmunoassay (RIA). Enzymatically determined serum acid phosphatase was raised in only 38% of the same patients. Bone marrow acid phosphatase determined by RIA was raised in 41%. In untreated metastatic patients with prostatic carcinoma, radioimmunologically determined serum acid phosphatase was elevated in 12 of 13 patients, whereas bone marrow acid phosphatase (RIA) and enzymatically determined serum prostatic acid phosphatase were increased only in about half of the patients. In a control group the upper reference limit of bone marrow acid phosphatase determined by RIA was significantly raised above that obtained by serum analyses. This indicates that nonprostatic acid phosphatases (possibly from bone marrow cells) cross-react with prostatic acid phosphatase in an unpredictable way, even when using a specific radioimmunoassay. In patients with metastatic carcinoma of the prostate, the results of bone marrow acid phosphatase determinations, analysed by RIA, seem to lack diagnostic and/or prognostic information additional to that obtainable by serum acid phosphatase (RIA) analysis.