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ABPath Chemical Pathology study materials
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ABPath Chemical Pathology practice questions

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Question 1Laboratory administrative and management requirements and practices

Which document issued by a laboratory describes how it ensures the validity of its results and is used to communicate its competence to clients and regulators?

  1. The quality manual Correct answer.
  2. The scope of accreditation certificate
  3. The safety data sheet
  4. The internal audit schedule

Explanation

The quality manual is the top-level document describing the laboratory's quality management system, including how result validity is assured. Accreditation certificates list the accredited scope but do not describe processes. Audit schedules and safety data sheets serve narrower purposes.

Question 2Laboratory administrative and management requirements and practices

A laboratory reports results in SI units while a requesting clinician uses conventional units. Which practice best supports safe interpretation of the report?

  1. Rounding all results to whole numbers
  2. Omitting units to reduce confusion
  3. Providing the reference interval and unit alongside each result Correct answer.
  4. Reporting only SI units with no conversion information

Explanation

Including the unit and the applicable reference interval on the report allows the reader to interpret the result regardless of the unit system used. Omitting units or conversion aids increases the risk of misinterpretation.

Question 3Laboratory administrative and management requirements and practices

Which of the following is the primary purpose of an external quality assessment (proficiency testing) scheme?

  1. To compare a laboratory's performance with that of peer laboratories Correct answer.
  2. To verify staff competency records
  3. To replace internal quality control for all analytes
  4. To calibrate analytical instruments

Explanation

External quality assessment provides interlaboratory comparison so a laboratory can judge its performance against peers and reference methods. It complements, but does not replace, internal quality control.

Question 4Laboratory administrative and management requirements and practices

Which body publishes the international standard specifying general requirements for the competence of medical laboratories?

  1. WHO
  2. ISO Correct answer.
  3. CLSI
  4. CAP

Explanation

ISO 15189 is the international standard for medical laboratory competence and quality, published by the International Organization for Standardization. CLSI and CAP produce guidance and accreditation programs but not this international standard.

Question 5Laboratory administrative and management requirements and practices

Which record is most important for demonstrating traceability of a patient result back to the specimen and analysis?

  1. The staff holiday roster
  2. The specimen accession log with unique identifiers Correct answer.
  3. The equipment purchase invoice
  4. The chemical inventory list

Explanation

A specimen accession log linking a unique identifier to the patient, collection, and analysis events provides the audit trail required for traceability. Financial and staffing records do not establish this link.

Question 6Laboratory administrative and management requirements and practices

A laboratory introduces a new analyzer and must verify that results agree with the current method before going live. Which activity is required?

  1. A review of the manufacturer's brochure
  2. A method comparison study using patient samples spanning the measuring interval Correct answer.
  3. A staff satisfaction survey
  4. A single replicate of a calibrator

Explanation

Method verification requires comparison against the existing or reference method across the clinically relevant range using patient samples. A single calibrator replicate or marketing material does not demonstrate comparability.

Question 7Laboratory administrative and management requirements and practices

Under a typical laboratory quality system, which of the following best describes a corrective action?

  1. An action taken to eliminate the cause of a detected nonconformity Correct answer.
  2. A routine equipment maintenance task
  3. A scheduled staff training session
  4. A planned activity to prevent a potential problem from occurring

Explanation

A corrective action addresses the root cause of a nonconformity that has already occurred, to prevent recurrence. Preventive action addresses a potential problem before it happens.

Question 8Laboratory administrative and management requirements and practices

A laboratory's internal quality control shows a shift in the mean of a control over several runs. Which is the most appropriate initial management step?

  1. Discarding the control material
  2. Reviewing control charts and investigating possible causes before releasing affected results Correct answer.
  3. Recalibrating without documenting the event
  4. Immediately reporting patient results without review

Explanation

A shift indicates a systematic change, so the laboratory should review control data and investigate causes such as reagent lot changes or calibration drift before releasing results. Undocumented or premature actions undermine the quality system.

Question 9Laboratory administrative and management requirements and practices

Which of the following is the best example of a key performance indicator for the preanalytical phase of laboratory testing?

  1. Number of analyzer calibrations performed
  2. Frequency of external quality assessment surveys
  3. Turnaround time for instrument maintenance
  4. Percentage of specimens rejected due to hemolysis or insufficient volume Correct answer.

Explanation

Specimen rejection rates reflect preanalytical quality, which covers collection, transport, and receipt. Calibration and maintenance relate to the analytical phase, and EQA frequency is a program characteristic.

Question 10Laboratory administrative and management requirements and practices

A clinician requests a test that is not on the laboratory's accredited scope. What is the most appropriate laboratory response?

  1. Perform the test if validated and clearly indicate its accreditation status Correct answer.
  2. Perform the test and report it as accredited
  3. Refer the request to the purchasing department
  4. Decline all communication about the test

Explanation

A laboratory may perform validated tests outside its accredited scope but must not imply accreditation for them. Clear communication of accreditation status maintains transparency with users.

Question 11Laboratory administrative and management requirements and practices

Which element is essential in a laboratory's document control system?

  1. Ensuring only current approved versions are available at points of use Correct answer.
  2. Storing documents only on personal devices
  3. Removing version numbers to simplify filing
  4. Allowing uncontrolled copies to circulate freely

Explanation

Document control ensures that only current, approved versions are accessible where work is performed and that obsolete documents are removed or marked. Uncontrolled copies and missing version identifiers defeat this purpose.

Question 12Laboratory administrative and management requirements and practices

A laboratory must validate a new lot of reagent before use. Which approach best demonstrates acceptability?

  1. Comparing results with the previous lot using quality control and patient samples Correct answer.
  2. Checking the color of the reagent vial
  3. Using the lot for one patient and accepting the result
  4. Relying solely on the manufacturer's certificate of analysis

Explanation

Lot-to-lot verification compares the new lot with the previous one using QC and patient samples to confirm comparable performance. A certificate of analysis alone does not demonstrate local performance.

Question 13Laboratory administrative and management requirements and practices

Which activity is the main purpose of a laboratory internal audit?

  1. To discipline staff who make errors
  2. To verify that processes comply with planned arrangements and are effectively implemented Correct answer.
  3. To replace external accreditation assessment
  4. To reduce the number of staff required

Explanation

Internal audits independently verify that the quality system conforms to planned arrangements and is effectively implemented. They are not disciplinary tools and do not substitute for external assessment.

Question 14Laboratory administrative and management requirements and practices

A laboratory reports a critical (panic) result. Which practice best meets good laboratory management requirements?

  1. Recording the notification with the time, recipient, and result communicated Correct answer.
  2. Waiting until the next routine report is issued
  3. Omitting documentation to save time
  4. Sending the result by routine mail only

Explanation

Critical results require timely communication with documentation of who was notified, when, and what was communicated, providing an audit trail. Routine or delayed communication defeats the purpose of critical value reporting.

Question 15Laboratory administrative and management requirements and practices

Which of the following best describes the concept of measurement uncertainty in laboratory reporting?

  1. The guaranteed absence of any analytical error
  2. The time taken to perform an assay
  3. A parameter characterizing the dispersion of values attributable to the measurand Correct answer.
  4. The number of samples rejected per month

Explanation

Measurement uncertainty is a quantitative estimate of the dispersion of results that can reasonably be attributed to the measurand, derived from precision and bias data. It does not imply zero error and is unrelated to turnaround time or rejection counts.

Question 16Laboratory administrative and management requirements and practices

A laboratory is planning a change to its reporting software. Which sequence best reflects sound change-control practice?

  1. Delegate approval to the software vendor alone
  2. Implement the change, then inform users and document afterward
  3. Implement without testing to save time
  4. Assess risk, validate the change, obtain approval, then implement with documentation Correct answer.

Explanation

Change control requires risk assessment, validation, documented approval, and controlled implementation so that changes do not compromise result integrity. Retrospective documentation or vendor-only approval does not satisfy this requirement.

Question 17Laboratory administrative and management requirements and practices

A laboratory identifies that a recurring nonconformity keeps reappearing despite repeated corrective actions. Which approach is most appropriate?

  1. Performing a root cause analysis and verifying effectiveness of the action Correct answer.
  2. Closing the issue as resolved to reduce backlog
  3. Ignoring it because it is recurrent
  4. Blaming individual staff members

Explanation

Recurring nonconformities indicate that the underlying cause has not been addressed, so a structured root cause analysis followed by effectiveness verification is required. Closing or ignoring the issue violates quality management principles.

Question 18Patient preparation and specimen collection

A patient is scheduled for a morning fasting blood glucose. Which instruction best reflects standard fasting requirements?

  1. No caloric intake for at least 8 hours, water permitted Correct answer.
  2. No food or water for at least 12 hours
  3. Only caffeinated drinks should be avoided before the draw
  4. A light breakfast is acceptable if it contains no sugar

Explanation

Standard fasting for glucose and lipids requires no caloric intake for roughly 8 to 12 hours, while plain water is allowed and does not affect results. Complete water restriction is unnecessary and can cause hemoconcentration.

Question 19Patient preparation and specimen collection

Which blood collection tube additive is preferred for measuring plasma glucose when immediate analysis is not possible?

  1. Plain serum tube with clot activator
  2. Lithium heparin without preservative
  3. Sodium citrate
  4. Sodium fluoride with potassium oxalate Correct answer.

Explanation

Fluoride inhibits glycolysis in the collected cells, preserving glucose concentrations during transport and delay. Oxalate acts as an anticoagulant in this combination tube.

Question 20Patient preparation and specimen collection

For accurate measurement of ionized calcium, which pre-analytical condition is most important?

  1. Drawing the sample after prolonged fist clenching
  2. Anaerobic handling and minimal tourniquet time Correct answer.
  3. Storing the sample at room temperature for several hours
  4. Collecting the sample in a citrate tube

Explanation

Ionized calcium is sensitive to pH, so anaerobic handling prevents carbon dioxide loss and pH shift. Prolonged tourniquet use and fist clenching raise pH and alter ionized calcium results.

Question 21Patient preparation and specimen collection

A 24-hour urine collection for metanephrines is being arranged. Which instruction is most appropriate during the collection period?

  1. Increase fluid intake to at least four liters daily
  2. Store the container at room temperature throughout
  3. Avoid catecholamine-rich foods such as coffee, tea, and bananas Correct answer.
  4. Discard the first morning void and all subsequent voids

Explanation

Dietary catecholamines and their precursors can falsely elevate metanephrine results, so foods such as coffee, tea, bananas, and chocolate are typically restricted. The container is usually refrigerated and acidified depending on the analyte.

Question 22Patient preparation and specimen collection

Which practice best reduces the risk of hemolysis during venipuncture?

  1. Using a large-bore needle and avoiding excessive suction Correct answer.
  2. Drawing blood through a small-gauge needle with vigorous aspiration
  3. Shaking the tube vigorously after collection
  4. Forcing blood through a needle into a syringe after a failed draw

Explanation

Hemolysis is reduced by using appropriately sized needles, avoiding excessive vacuum and turbulence, and not forcing blood through small openings. Vigorous mixing or aspiration increases red cell rupture.

Question 23Patient preparation and specimen collection

A patient is having blood drawn for therapeutic drug monitoring of an aminoglycoside. Which timing principle applies to a trough level?

  1. Collect just before the next dose is administered Correct answer.
  2. Collect immediately after the dose is given
  3. Collect two hours after the infusion ends
  4. Collect at any time because aminoglycoside levels are time-independent

Explanation

Trough concentrations are measured immediately before the next scheduled dose to reflect the lowest steady-state level. Peak levels are drawn at a defined interval after the dose.

Question 24Patient preparation and specimen collection

Which specimen type is required for measuring ammonia in a patient with suspected hepatic encephalopathy?

  1. Urine collected as a random sample
  2. Serum collected in a plain tube and left at room temperature
  3. Plasma collected in an EDTA tube placed immediately on ice Correct answer.
  4. Whole blood stored at 37 degrees Celsius for one hour

Explanation

Ammonia requires rapid processing because red cells release ammonia and in vitro production continues after collection. EDTA plasma placed on ice and analyzed promptly minimizes pre-analytical error.

Question 25Patient preparation and specimen collection

A patient reports having eaten a large meal two hours before a scheduled lipid panel. Which action is most appropriate?

  1. Proceed with the draw and report results as fasting
  2. Add a postprandial glucose to the request
  3. Draw the sample and correct the triglycerides mathematically
  4. Reschedule the draw to allow an adequate fasting interval Correct answer.

Explanation

Triglycerides rise substantially after a meal, so a fasting specimen is required for a valid fasting lipid panel. Rescheduling is the appropriate action rather than attempting to correct results.

Question 26Patient preparation and specimen collection

When collecting blood cultures from an adult, which approach best supports optimal recovery of organisms?

  1. Collect two or more sets from separate sites before antibiotics Correct answer.
  2. Collect a single bottle with a small volume of blood
  3. Collect after antibiotics have been administered
  4. Collect both sets from the same venipuncture using one needle

Explanation

Multiple sets from separate sites increase sensitivity and help distinguish contamination from true bacteremia. Collection before antimicrobial therapy maximizes organism recovery.

Question 27Patient preparation and specimen collection

Which collection order is correct when drawing multiple tubes by the standard order of draw?

  1. Citrate, serum, heparin, EDTA Correct answer.
  2. EDTA, citrate, serum, heparin
  3. Serum, citrate, EDTA, heparin
  4. Heparin, EDTA, citrate, serum

Explanation

The standard order of draw places coagulation (citrate) tubes first to avoid contamination with other additives, followed by serum, heparin, and EDTA tubes. This sequence minimizes additive carryover that could alter results.

Question 28Patient preparation and specimen collection

A capillary blood gas sample is being collected from an infant's heel. Which practice improves accuracy?

  1. Collecting from the central area of the heel pad
  2. Warming the heel before puncture and avoiding squeezing Correct answer.
  3. Squeezing the heel firmly to obtain sufficient blood
  4. Allowing the sample to stand open to air before analysis

Explanation

Warming the heel improves perfusion, and avoiding squeezing prevents hemolysis and tissue fluid contamination. Puncturing the central heel risks injury to the calcaneus.

Question 29Patient preparation and specimen collection

A patient's serum sample shows markedly elevated potassium with no clinical signs of hyperkalemia, and the specimen was collected with prolonged tourniquet use and fist clenching. Which is the most likely explanation?

  1. Pseudohyperkalemia from pre-analytical factors Correct answer.
  2. Specimen dilution from intravenous fluid contamination
  3. True hyperkalemia requiring urgent treatment
  4. Analytical interference from hemolysis-resistant assay

Explanation

Prolonged tourniquet use and fist clenching raise local potassium release from muscle, producing pseudohyperkalemia. Recollection with standardized technique is needed to confirm the result.

Question 30Patient preparation and specimen collection

Which instruction should be given to a patient before a plasma renin and aldosterone measurement to reduce confounding?

  1. Take the sample after a large caffeine-containing meal
  2. Discuss holding interfering medications and note posture requirements Correct answer.
  3. Perform vigorous exercise immediately before the draw
  4. Maintain a high-sodium diet for three days before testing

Explanation

Renin and aldosterone are influenced by sodium balance, posture, and medications such as mineralocorticoid receptor antagonists. Standardized posture and medication review reduce variability.

Question 31Patient preparation and specimen collection

A 24-hour urine collection for creatinine clearance is being evaluated. The patient reports discarding the first morning void on day one and missing the final void on day two. How should this be interpreted?

  1. The collection is complete and suitable for calculation
  2. The result can be corrected by adjusting for body surface area
  3. The collection is incomplete and should be repeated Correct answer.
  4. The missing void is acceptable if the total volume is recorded

Explanation

A complete 24-hour collection begins after discarding the first morning void and includes the first void of the following morning. Missing the final void makes the collection incomplete and invalid for clearance calculation.

Question 32Patient preparation and specimen collection

Which condition most strongly requires that a specimen for plasma free metanephrines be collected with the patient supine and after an appropriate rest period?

  1. Screening for iron deficiency
  2. Therapeutic monitoring of vancomycin
  3. Routine liver function assessment
  4. Suspected pheochromocytoma evaluation Correct answer.

Explanation

Plasma free metanephrines are sensitive to sympathetic activation, and upright posture increases values. Supine sampling after rest reduces false-positive elevations in pheochromocytoma evaluation.

Question 33Patient preparation and specimen collection

A patient is receiving intravenous fluids through a forearm cannula, and blood is drawn from the same arm distal to the cannula. Which is the most likely effect on the results?

  1. Dilution of analytes by infused fluid Correct answer.
  2. Falsely high glucose from glycolysis inhibition
  3. No effect because the cannula is proximal
  4. Falsely low potassium from chelation

Explanation

Drawing blood distal to an infusion site can contaminate the specimen with infusate, diluting analytes and altering electrolyte results. Blood should be drawn from the opposite arm or after appropriate line flushing and discard.

Question 34Patient preparation and specimen collection

A laboratory receives a grossly lipemic sample for electrolyte measurement. Which pre-analytical issue should be considered when interpreting the sodium result?

  1. Falsely low chloride from lipid interference
  2. Falsely high bicarbonate from lipemia
  3. Pseudohyponatremia from hyperlipidemia with certain methods Correct answer.
  4. No interference with any electrolyte method

Explanation

Severe lipemia can cause pseudohyponatremia with indirect ion-selective electrode methods because the aqueous phase is displaced by excess lipid. Direct ion-selective electrode methods are less affected.

Question 35Standards and units of measurement

Which SI base unit is used to express the amount of substance in a clinical sample?

  1. The mole Correct answer.
  2. The gram
  3. The litre
  4. The newton

Explanation

The mole is the SI base unit for amount of substance and is defined by a fixed number of elementary entities. Mass (gram) and volume (litre) are not base units for amount of substance.

Question 36Standards and units of measurement

A plasma glucose result is reported as 5.5 mmol/L. What is this concentration expressed in µmol/L?

  1. 550 µmol/L
  2. 55 000 µmol/L
  3. 5500 µmol/L Correct answer.
  4. 55 µmol/L

Explanation

One millimole equals 1000 micromoles, so 5.5 mmol/L becomes 5.5 × 1000 = 5500 µmol/L. Conversion between metric prefixes moves the decimal three places per step.

Question 37Standards and units of measurement

Which prefix denotes a factor of 10⁻⁹?

  1. Pico
  2. Micro
  3. Femto
  4. Nano Correct answer.

Explanation

Nano represents 10⁻⁹, micro represents 10⁻⁶, pico represents 10⁻¹² and femto represents 10⁻¹⁵. The prefixes descend in steps of a thousand.

Question 38Standards and units of measurement

A creatinine result is 1.2 mg/dL. Given a molar mass of 113 g/mol, what is the approximate concentration in µmol/L?

  1. 10 600 µmol/L
  2. 106 µmol/L Correct answer.
  3. 1060 µmol/L
  4. 10.6 µmol/L

Explanation

Convert mg/dL to mg/L by multiplying by 10 (12 mg/L), then divide by molar mass in g/mol and multiply by 1000 to reach µmol/L: 12 ÷ 113 × 1000 ≈ 106 µmol/L. Remember that 1 mg/dL equals 10 mg/L.

Question 39Standards and units of measurement

In clinical chemistry, which term strictly describes the amount of a substance in relation to the volume of the solution?

  1. Osmolality
  2. Molarity Correct answer.
  3. Normality
  4. Molality

Explanation

Molarity expresses moles of solute per litre of solution. Molality and osmolality are both defined per kilogram of solvent, and normality depends on reactive equivalents.

Question 40Standards and units of measurement

A laboratory reports a calcium of 2.50 mmol/L. What is this value in mg/dL? (Molar mass of calcium = 40 g/mol; 1 mg/dL = 10 mg/L.)

  1. 1.0 mg/dL
  2. 6.25 mg/dL
  3. 10.0 mg/dL Correct answer.
  4. 25.0 mg/dL

Explanation

2.50 mmol/L equals 2.5 × 40 = 100 mg/L, which divided by 10 gives 10 mg/dL. The molar mass converts millimoles to milligrams, and the volume factor converts per litre to per decilitre.

Question 41Standards and units of measurement

Which statement correctly describes the relationship between osmolarity and osmolality in plasma?

  1. Osmolarity exceeds osmolality because plasma contains dissolved protein
  2. Osmolality is measured in osmoles per litre of solution
  3. Osmolarity and osmolality are numerically identical in all biological fluids
  4. Osmolality exceeds osmolarity because plasma water is less than plasma volume Correct answer.

Explanation

Osmolality is osmoles per kilogram of water, whereas osmolarity is osmoles per litre of solution. Because plasma is about 93% water, the same number of particles is distributed in a smaller water mass, giving a higher osmolality.

Question 42Standards and units of measurement

A result is reported as 0.85 mmol/L with an uncertainty of ±0.05 mmol/L. Which statement best describes this uncertainty?

  1. It represents the total error contributed only by the calibrator
  2. It is the difference between the highest and lowest replicate results
  3. It defines an interval within which the true value is expected to lie Correct answer.
  4. It is the maximum value the analyser can measure

Explanation

Measurement uncertainty defines an interval around the reported result within which the true value is expected to lie with a stated level of confidence. It combines all sources of error rather than any single component.

Question 43Standards and units of measurement

According to the SI definition, which of the following is a derived unit?

  1. The kelvin
  2. The joule Correct answer.
  3. The second
  4. The mole

Explanation

The joule is a derived SI unit, defined as kg·m²·s⁻². Kelvin, second and mole are base units in the SI system.

Question 44Standards and units of measurement

A laboratory wishes to report enzyme activity in SI units. Which unit is correct?

  1. Katal per litre (kat/L) Correct answer.
  2. International units per litre (IU/L)
  3. Milligrams per decilitre (mg/dL)
  4. Milliosmoles per kilogram (mOsm/kg)

Explanation

The katal is the SI derived unit of catalytic activity, defined as one mole of substrate converted per second. International units per litre express activity in micromoles per minute and are not SI.

Question 45Standards and units of measurement

A 24-hour urine collection of 2.0 L contains 8.0 mmol of a metabolite. What is the excretion rate per 24 hours if the result is expressed in µmol/24 h?

  1. 16 000 µmol/24 h
  2. 8000 µmol/24 h Correct answer.
  3. 4000 µmol/24 h
  4. 400 µmol/24 h

Explanation

The total amount is 8.0 mmol, and 1 mmol equals 1000 µmol, giving 8000 µmol in the 24-hour collection. The volume is already accounted for because the total amount is stated.

Question 46Standards and units of measurement

Which statement about the reference interval for a laboratory test is correct?

  1. It represents the range within which all healthy individuals must fall
  2. It is identical to the analytical measuring range of the method
  3. It is derived from the results of the population being tested
  4. It typically encompasses the central 95% of a healthy reference population Correct answer.

Explanation

A reference interval is conventionally calculated to include the central 95% of results from a defined healthy reference population. By construction, about 5% of healthy individuals fall outside it.

Question 47Standards and units of measurement

A method is calibrated in SI units but a clinician requests results in conventional units. Which action best preserves the integrity of reporting?

  1. Recalibrate the analyser to conventional units for that specimen
  2. Apply a documented, method-specific conversion factor and state the units used Correct answer.
  3. Round both unit systems to the nearest whole number
  4. Report the SI value and let the clinician perform the conversion

Explanation

Converting between unit systems should use a documented, validated factor with the units clearly stated, preserving traceability. Ad hoc recalibration or leaving conversion to the requester introduces error and ambiguity.

Question 48Standards and units of measurement

A sodium result is 140 mmol/L. How many milliosmoles of sodium per litre does this represent, given sodium is the principal extracellular cation?

  1. 280 mOsm/L
  2. 140 mOsm/L Correct answer.
  3. 14 mOsm/L
  4. 70 mOsm/L

Explanation

Sodium is monovalent, so 1 mmol of sodium contributes 1 mOsm of osmotic particles. A concentration of 140 mmol/L therefore contributes 140 mOsm/L of sodium-associated osmolality.

Question 49Standards and units of measurement

A laboratory reports a troponin result of 12 ng/L. What is this in µg/L?

  1. 1.2 µg/L
  2. 0.012 µg/L Correct answer.
  3. 0.12 µg/L
  4. 120 µg/L

Explanation

One microgram equals 1000 nanograms, so 12 ng/L divided by 1000 gives 0.012 µg/L. Moving from nano to micro requires dividing by a thousand.

Question 50Standards and units of measurement

A laboratory wants to harmonise reporting of a hormone assay with other centres. Which approach best supports comparability of results?

  1. Expressing results as a ratio to a local pooled sample
  2. Traceable calibration to an internationally agreed reference preparation Correct answer.
  3. Reporting in arbitrary units specific to the local analyser
  4. Reporting only the raw signal from the detection system

Explanation

Comparability across laboratories requires calibration traceable to a common international reference preparation or reference measurement procedure. Local arbitrary units, ratios or raw signals cannot be compared between centres.