Marinus A. Blankenstein

CSF Biomarkers and Incipient Alzheimer Disease in Patients With Mild Cognitive Impairment

CONTEXT Small single-center studies have shown that cerebrospinal fluid (CSF) biomarkers may be useful to identify incipient Alzheimer disease (AD) in patients with mild cognitive impairment (MCI), but large-scale multicenter studies have not been conducted. OBJECTIVE To determine the diagnostic accuracy of CSF beta-amyloid(1-42) (Abeta42), total tau protein (T-tau), and tau phosphorylated at position threonine 181 (P-tau) for predicting incipient AD in patients with MCI. DESIGN, SETTING, AND PARTICIPANTS The study had 2 parts: a cross-sectional study involving patients with AD and controls to identify cut points, followed by a prospective cohort study involving patients with MCI, conducted 1990-2007. A total of 750 individuals with MCI, 529 with AD, and 304 controls were recruited by 12 centers in Europe and the United States. Individuals with MCI were followed up for at least 2 years or until symptoms had progressed to clinical dementia. MAIN OUTCOME MEASURES Sensitivity, specificity, positive and negative likelihood ratios (LRs) of CSF Abeta42, T-tau, and P-tau for identifying incipient AD. RESULTS During follow-up, 271 participants with MCI were diagnosed with AD and 59 with other dementias. The Abeta42 assay in particular had considerable intersite variability. Patients who developed AD had lower median Abeta42 (356; range, 96-1075 ng/L) and higher P-tau (81; range, 15-183 ng/L) and T-tau (582; range, 83-2174 ng/L) levels than MCI patients who did not develop AD during follow-up (579; range, 121-1420 ng/L for Abeta42; 53; range, 15-163 ng/L for P-tau; and 294; range, 31-2483 ng/L for T-tau, P < .001). The area under the receiver operating characteristic curve was 0.78 (95% confidence interval [CI], 0.75-0.82) for Abeta42, 0.76 (95% CI, 0.72-0.80) for P-tau, and 0.79 (95% CI, 0.76-0.83) for T-tau. Cut-offs with sensitivity set to 85% were defined in the AD and control groups and tested in the MCI group, where the combination of Abeta42/P-tau ratio and T-tau identified incipient AD with a sensitivity of 83% (95% CI, 78%-88%), specificity 72% (95% CI, 68%-76%), positive LR, 3.0 (95% CI, 2.5-3.4), and negative LR, 0.24 (95% CI, 0.21-0.28). The positive predictive value was 62% and the negative predictive value was 88%. CONCLUSIONS This multicenter study found that CSF Abeta42, T-tau, and P-tau identify incipient AD with good accuracy, but less accurately than reported from single-center studies. Intersite assay variability highlights a need for standardization of analytical techniques and clinical procedures.

The Alzheimer's Association external quality control program for cerebrospinal fluid biomarkers.

The cerebrospinal fluid (CSF) biomarkers amyloid β (Aβ)‐42, total‐tau (T‐tau), and phosphorylated‐tau (P‐tau) demonstrate good diagnostic accuracy for Alzheimers disease (AD). However, there are large variations in biomarker measurements between studies, and between and within laboratories. The Alzheimers Association has initiated a global quality control program to estimate and monitor variability of measurements, quantify batch‐to‐batch assay variations, and identify sources of variability. In this article, we present the results from the first two rounds of the program.

Accuracy of 6 Routine 25-Hydroxyvitamin D Assays: Influence of Vitamin D Binding Protein Concentration

BACKGROUND Recent recognition of its broad pathophysiological importance has triggered an increased interest in 25-hydroxyvitamin D [25(OH)D]. By consequence, throughput in 25(OH)D testing has become an issue for clinical laboratories, and several automated assays for measurement of 25(OH)D are now available. The aim of this study was to test the accuracy and robustness of these assays by comparing their results to those of an isotope dilution/online solid-phase extraction liquid chromatography/tandem mass spectrometry (ID-XLC-MS/MS) method. We put specific focus on the influence of vitamin D-binding protein (DBP) by using samples with various concentrations of DBP. METHODS We used 5 automated assays (Architect, Centaur, iSYS, Liaison, and Elecsys), 1 RIA (Diasorin) preceded by extraction, and an ID-XLC-MS/MS method to measure 25(OH)D concentrations in plasma samples of 51 healthy individuals, 52 pregnant women, 50 hemodialysis patients, and 50 intensive care patients. Using ELISA, we also measured DBP concentrations in these samples. RESULTS Most of the examined 25(OH)D assays showed significant deviations in 25(OH)D concentrations from those of the ID-XLC-MS/MS method. As expected, DBP concentrations were higher in samples of pregnant women and lower in samples of IC patients compared to healthy controls. In 4 of the 5 fully automated 25(OH)D assays, we observed an inverse relationship between DBP concentrations and deviations from the ID-XLC-MS/MS results. CONCLUSIONS 25(OH)D measurements performed with most immunoassays suffer from inaccuracies that are DBP concentration dependent. Therefore, when interpreting results of 25(OH)D measurements, careful consideration of the measurement method is necessary.

The cardiovascular risk factor plasminogen activator inhibitor type 1 is related to insulin resistance

The cardiovascular risk factor plasminogen activator inhibitor type 1 (PAI-1) has been associated with abdominal obesity, hypertension, hypertriglyceridemia, hyperinsulinemia, glucose intolerance, and type II diabetes, conditions known to be linked with insulin resistance. To determine whether PAI-1 is related to insulin resistance, we studied nine obese nondiabetics and 10 obese type II diabetics by means of a sequential hyperinsulinemic euglycemic clamp study. Plasma PAI-1 antigen (Ag) correlated significantly with peripheral insulin resistance, represented by the insulin level at which peripheral glucose uptake (PGU) is half-maximal ([ED50PGU] r = .87, P < .001). Multiple regression analysis including indices of hepatic and peripheral insulin action, fasting plasma insulin levels, triglyceride levels, blood pressure (BP), waist to hip ratio (WHR), and body mass index (BMI) disclosed ED50PGU to account for 76% of the variance of PAI-1 Ag. We suggest that PAI-1 contributes to the increased cardiovascular risk encountered with insulin resistance.

Amyloid-β(1–42), Total Tau, and Phosphorylated Tau as Cerebrospinal Fluid Biomarkers for the Diagnosis of Alzheimer Disease

BACKGROUND To improve ante mortem diagnostic accuracy of Alzheimer disease (AD), measurement of the biomarkers amyloid-beta(1-42) (Abeta42), total tau (Tau), and tau phosphorylated at threonine(181) (pTau) in cerebrospinal fluid (CSF) has been proposed. We have used these markers and evaluated their performance. METHODS From January 2001 to January 2007, we assessed Abeta42, Tau, and pTau by commercial ELISAs in CSF from 248 consecutive AD patients and 131 patients with subjective memory complaints attending our outpatient memory clinic. Diagnoses were made blind to the results of the biomarker assays. We assessed sensitivity and specificity and analyzed trends over time. RESULTS Interassay CVs from analysis of pools of surplus CSF specimens were mean 11.3% (SD 4.9%) for Abeta42; 9.3% (1.5%) for Tau, and 9.4% (2.5%) for pTau, respectively (n = 7-18). To achieve 85% sensitivity, cutoff values were 550 (95% CI 531-570) ng/L for Abeta42; 375 (325-405) ng/L for Tau, and 52 (48-56) ng/L for pTau. Corresponding specificities were 83% (95% CI 76%-89%) for Abeta42, 78% (70%-85%) for Tau, and 68% (60%-77%) for pTau. Logistic regression to investigate the simultaneous impact of the 3 CSF biomarkers on the diagnosis yielded a sensitivity of 93.5% and specificity of 82.7%, at a discrimination line of Abeta42 = 373 + 0.82 x Tau. The area under the ROC curves of Tau and pTau showed significant fluctuation over time. CONCLUSIONS CSF biomarkers Abeta42 and Tau can be used as a diagnostic aid in AD. pTau did not have additional value over these 2 markers. Cutoff values, sensitivities, specificities, and discrimination lines depend on the patient groups studied and laboratory experience.

Cerebrospinal fluid markers for differential dementia diagnosis in a large memory clinic cohort

Objective: To determine how amyloid β 42 (Aβ42), total tau (t-tau), and phosphorylated tau (p-tau) levels in CSF behave in a large cohort of patients with different types of dementia. Methods: Baseline CSF was collected from 512 patients with Alzheimer disease (AD) and 272 patients with other types of dementia (OD), 135 patients with a psychiatric disorder (PSY), and 275 patients with subjective memory complaints (SMC). Aβ42, t-tau, and p-tau (at amino acid 181) were measured in CSF by ELISA. Autopsy was obtained in a subgroup of 17 patients. Results: A correct classification of patients with AD (92%) and patients with OD (66%) was accomplished when CSF Aβ42 and p-tau were combined. Patients with progressive supranuclear palsy had normal CSF biomarker values in 90%. Patients with Creutzfeldt-Jakob disease demonstrated an extremely high CSF t-tau at a relatively normal CSF p-tau. CSF AD biomarker profile was seen in 47% of patients with dementia with Lewy bodies (DLB), 38% in corticobasal degeneration (CBD), and almost 30% in frontotemporal lobar degeneration (FTLD) and vascular dementia (VaD). PSY and SMC patients had normal CSF biomarkers in 91% and 88%. Older patients are more likely to have a CSF AD profile. Concordance between clinical and neuropathologic diagnosis was 85%. CSF markers reflected neuropathology in 94%. Conclusion: CSF Aβ42, t-tau, and p-tau are useful in differential dementia diagnosis. However, in DLB, FTLD, VaD, and CBD, a substantial group exhibit a CSF AD biomarker profile, which requires more autopsy confirmation in the future.

Maternal segregation of the Dutch preeclampsia locus at 10q22 with a new member of the winged helix gene family.

Preeclampsia is a pregnancy-associated disease with maternal symptoms but placental origin. Epigenetic inheritance is involved in some populations. By sequence analysis of 17 genes in the 10q22 region with maternal effects, we narrowed the minimal critical region linked with preeclampsia in the Netherlands to 444 kb. All but one gene in this region, which lies within a female-specific recombination hotspot, encode DNA- or RNA-binding proteins. One gene, STOX1 (also called C10orf24), contained five different missense mutations, identical between affected sisters, cosegregating with the preeclamptic phenotype and following matrilineal inheritance. Four STOX1 transcripts are expressed in early placenta, including invasive extravillus trophoblast, generating three different isoforms. All contain a winged helix domain related to the forkhead (FOX) family. The largest STOX1 isoform has exclusive nuclear or cytoplasmic expression, indicating activation and inactivation, respectively, of the PI3K-Akt-FOX pathway. Because all 38 FOX proteins and all 8 STOX1 homologs have either tyrosine or phenylalanine at position 153, the predominant Y153H variation is highly mutagenic by conservation criteria but subject to incomplete penetrance. STOX1 is a candidate for preeclampsia controlling polyploidization of extravillus trophoblast.

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

Background Different cerebrospinal fluid (CSF) amyloid-beta 1–42 (Aβ 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 Aβ 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 Aβ 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 Aβ 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 Aβ 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.

CSF biomarkers and medial temporal lobe atrophy predict dementia in mild cognitive impairment

OBJECTIVE To study CSF biomarkers, beta-amyloid(1-42) (Abeta(1-42)) and tau, and medial temporal lobe atrophy (MTA) on MRI in their ability to predict dementia in patients with mild cognitive impairment (MCI). METHODS Fifty-nine MCI patients (49% male, mean age 69+/-8), follow-up 19 months, were included. Baseline CSF levels of Abeta(1-42), tau and MTA-score were dichotomized. RESULTS Thirty-three (56%) of the MCI patients progressed to dementia, 30 of which had Alzheimers disease. Lower CSF Abeta(1-42) level, higher CSF-tau and higher MTA-scores at baseline were found in progressed patients. Cox proportional hazards models revealed that abnormal CSF Abeta(1-42), CSF tau and MTA were significantly associated with dementia at follow-up (hazard ratio (95% confidence interval): 4.0 (1.3-12.1), 5.9 (1.6-21.7) and 2.1 (1.0-4.6)). A fourfold higher risk was found for patients with both abnormal CSF biomarkers and MTA compared to patients with either test abnormal. Ninety-four percent of patients with both abnormalities converted to dementia. CONCLUSIONS These findings suggest an added value of CSF to MRI in the diagnostic work up of patients presenting at a memory clinic.

Elevated C-reactive protein levels during first trimester of pregnancy are indicative of preeclampsia and intrauterine growth restriction

C-reactive protein (CRP) is a marker of tissue damage and inflammation. Maternal levels of CRP are elevated in overt preeclampsia, but there is still debate about its use as a predictive marker for preeclampsia during the first and second trimesters of pregnancy. In this study, we measured CRP levels during the first trimester of pregnancy in women who later developed preeclampsia or gave birth to a growth-restricted baby. In total, 107 women from a low-risk population participated in the study, six women developed preeclampsia and nine gave birth to a growth-restricted baby. Although there is a large overlap in measured CRP levels between the three groups, mean CRP levels were significantly elevated in women who later developed preeclampsia (P=0.031) or delivered a growth-restricted baby (P=0.041) when compared with women from the control group, matched for maternal and gestational age, parity, and gravidity. This study shows that in a low-risk population, CRP levels are already elevated between weeks 10 and 14 in pregnant women who develop preeclampsia or deliver a growth-restricted baby.