Beta-Amyloid (1-42), CSF

Panels that include this biomarker

• Alzheimer's Disease Evaluation Profile, CSF 484415

  5 analytes · Csf · Fasting not stated · Turnaround 2 - 4 days

  Method and collection

  Method

  Roche Diagnostics Electrochemiluminescence Immunoassay (ECLIA)

  Collection

  Only the specimen listed below is acceptable for use with this assay. Please follow the steps listed below for CSF sample collection and measurement. Perform lumbar puncture (LP) using gravity drip collection method. • Avoid the use of syringes or tubings. • Perform lumbar puncture (LP) before noon. Do not use the first 2 mL of CSF for AD Biomarker measurement. Subsequently, collect at least 1.0 mL of CSF directly into the CSF tube 63.614.625 (Sarstedt) for AD biomarker measurements. • ( Note: The mark on the tube indicates 2.5 mL.) • Each sample should be visually inspected for hemolysis. • Do not use CSF samples that appear reddish for measurement of Elecsys AD biomarkers. • Instead, collect additional clear (non-hemolytic) CSF in a new CSF tube. Collection of CSF for other purposes can follow thereafter, if required. Do not process the CSF sample before transport to the measuring site (i.e., no mixing/inverting, no tube transfers, no aliquoting, no freezing and normally no centrifugation) until measurement. • It is strongly recommended that the sample be kept at 2‑8°C during transport and storage up to the time of measurement. • Samples can be stored at 2‑8°C for up to 14 days. • If transport and storage at 2‑8°C is not feasible, the sample can be transported/stored at room temperature (15‑25°C). If this is the case, measurement is to be performed within five days after sample draw.

  Reference notes

  β-Amyloid 1-42 (Abeta42), Total Tau (tTau) and Phospho‑Tau 181(pTau-181) are reported without reference intervals. The results from these three performed tests are used to calculate tTau/Abeta42 and the pTau-181/Abeta42 Ratios. Elecsys® tTau/Abeta42 ratio A negative result, defined as tTau/Abeta42 ratio value below cutoff or an Abeta42 value above the measuring range, is consistent with a negative amyloid positron emission tomography (PET) scan result. A negative result reduces the likelihood that a patient’s cognitive impairment is due to AD. A positive result, defined as tTau/Abeta42 ratio value above cutoff, is consistent with a positive amyloid PET scan result. Cutoff | tTau-181/Abeta42 ratio | Interpretation Cutoff (+)* | >0.28 | A positive result consistent with a positive amyloid PET scan result. Cutoff (-)† | ≤0.28 | A negative result consistent with a negative amyloid PET scan result. Invalid result for either or both Elecsys Total‑Tau CSF or Elecsys β‑Amyloid (1-42) CSFII results in tTau-181/Abeta42 ratio being reported with the abbreviation “UPTCAL,” which expands out to state: “Unable to calculate result since non-numeric result obtained for component test.” A positive result does not establish a diagnosis of AD or other cognitive disorder. The tTau-181/Abeta42 ratio result is used as an adjunct to other clinical diagnostic evaluations. Elecsys® pTau-181/Abeta42 ratio The Elecsys® pTau-181/Abeta42 ratio is highly concordant with amyloid PET and provides an alternative solution for detection of amyloid positivity.1,3 The Elecsys® pTau-181/Abeta42 ratio achieves 90% concordance with β-Amyloid PET scan results. A result above the cutoff is consistent with a positive amyloid PET visual read.1,3,9-11 The performance of the Elecsys® AD CSF ratio cutoff vs. amyloid PET visual read has been reported1,3,9 as such: pTau-181/Abeta42 ratio Cutoff (+)* | >0.023 Cutoff (-)† | ≤0.023 PPA% | 88.2 (84.4-91.2)‡ NPA% | 92.6 (89.1-95.1)‡ OPA% | 90.2(87.7-92.3)‡ • PPA: positive percent agreement • NPA: negative percent agreement • OPA: overall percent agreement *Consistent with positive amyloid PET scan result †Consistent with negative amyloid PET scan result ‡95% CI are calculated using a Wilson score method for binomial proportions Invalid result for either or both pTau-181 β‑Amyloid (1-42) results in tTau-181/Abeta42 ratio being reported with the abbreviation “UPTCAL,” which expands out to state: “Unable to calculate result since non-numeric result obtained for component test.” A negative result, defined as pTau-181/Abeta42 ratio value below cutoff or an Abeta42 value above the measuring range, is consistent with a negative amyloid positron emission tomography (PET) scan result.1,3 A negative result reduces the likelihood that a patient’s cognitive impairment is due to AD. A positive result, defined as pTau-181/Abeta42 ratio value above cutoff, is consistent with a positive amyloid PET scan result. A positive result does not establish a diagnosis of AD or other cognitive disorder. The pTau-181/Abeta42 ratio result is used as an adjunct to other clinical diagnostic evaluations.

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