I85PREP
⌘ K
ISCD CCD study materials
ISCD CCD study resources

ISCD CCD practice questions

One question at a time. Build your ISCD CCD understanding.

First 50 of 200 questions. Each one lists the choices, the correct answer, and an explanation. The checker at the top of this page saves progress in this browser when it is available.

Continue in the practice tool above to load more questions, 50 at a time.

Question 1Clinical Densitometry Knowledge and Skills

Which skeletal site is required for the lumbar spine measurement in a standard DXA study?

  1. L2 through L5
  2. L1 through L4 Correct answer.
  3. T12 through L5
  4. L1 through L5

Explanation

The standard lumbar spine region of interest for DXA includes vertebrae L1 through L4, and this is the default region used for diagnosis in most adults. Including additional vertebrae changes the reference values that apply.

Question 2Clinical Densitometry Knowledge and Skills

A T-score compares a patient's bone mineral density to which reference population?

  1. Age-, sex-, and ethnicity-matched peers
  2. The patient's prior measurement
  3. Premenopausal women only
  4. Young adult reference mean Correct answer.

Explanation

A T-score expresses BMD in standard deviations relative to the mean of a young adult reference population of the same sex. Z-scores, by contrast, use an age-matched reference.

Question 3Clinical Densitometry Knowledge and Skills

Which T-score at the femoral neck is classified as osteoporosis by the World Health Organization criterion?

  1. -1.5
  2. -2.0
  3. -2.5 Correct answer.
  4. -1.0

Explanation

The WHO classification defines osteoporosis as a T-score of -2.5 or lower at the hip or spine. Scores between -1.0 and -2.5 define osteopenia (low bone mass).

Question 4Clinical Densitometry Knowledge and Skills

When should a Z-score rather than a T-score be used for diagnostic classification?

  1. In children and premenopausal women Correct answer.
  2. In patients over age 65
  3. In men over age 50
  4. In patients with prior fracture

Explanation

Z-scores, which compare to age-matched peers, are the appropriate metric in children, premenopausal women, and men under 50. The diagnosis in these groups is based on a Z-score of -2.0 or lower plus clinical context.

Question 5Clinical Densitometry Knowledge and Skills

What does the least significant change (LSC) represent in DXA monitoring?

  1. The minimum T-score used for diagnosis
  2. The smallest BMD change considered statistically real Correct answer.
  3. The daily calibration drift of the densitometer
  4. The lowest BMD value a scanner can display

Explanation

The LSC is the magnitude of change between two measurements that exceeds measurement error at a chosen confidence level, typically 95%. Changes smaller than the LSC cannot be distinguished from precision error.

Question 6Clinical Densitometry Knowledge and Skills

Which artifact most commonly causes a falsely elevated lumbar spine BMD?

  1. Aortic calcification Correct answer.
  2. Overlying bowel gas
  3. Vertebral compression fracture
  4. Severe scoliosis

Explanation

Calcification of the abdominal aorta overlies the spine and adds mineral density to the measured region, falsely raising BMD. Compression fractures and scoliosis tend to lower or distort values.

Question 7Clinical Densitometry Knowledge and Skills

Which forearm site is conventionally used for the distal forearm measurement in DXA?

  1. 33% radius Correct answer.
  2. Ultradistal radius
  3. Radial tuberosity
  4. Midshaft ulna

Explanation

The one-third (33%) radius is the standard forearm site because it is predominantly cortical bone and has good precision. It is also the site recommended when hip and spine cannot be measured.

Question 8Clinical Densitometry Knowledge and Skills

Which statement correctly describes the relationship between BMD measured in g/cm² and areal bone density?

  1. It equals true volumetric density
  2. It represents mineral mass per projected area Correct answer.
  3. It corrects for bone depth
  4. It is independent of bone size

Explanation

DXA is a two-dimensional technique, so it reports areal BMD as mineral mass divided by projected area rather than true volumetric density. This makes values dependent on bone size and thickness.

Question 9Clinical Densitometry Knowledge and Skills

A 62-year-old woman has spine T-score -2.6 and hip T-score -2.2. According to ISCD principles, which value should be used for diagnosis?

  1. The spine value of -2.6 Correct answer.
  2. The hip value of -2.2
  3. The lower of the two values regardless of site
  4. The average of the two values

Explanation

The diagnosis uses the lowest T-score among valid measured sites, so the spine value of -2.6 establishes osteoporosis here. Averaging sites is not a valid approach.

Question 10Clinical Densitometry Knowledge and Skills

A spine DXA shows L1-L4 values but L3 is markedly higher than adjacent vertebrae and shows sclerosis on radiograph. What is the most appropriate action?

  1. Include L3 and report the average
  2. Repeat the scan at another facility
  3. Change the diagnosis to normal
  4. Exclude L3 and use the remaining vertebrae Correct answer.

Explanation

Vertebrae with focal structural change such as sclerosis or fracture should be excluded from analysis because they distort the regional BMD. The remaining valid vertebrae are used, provided at least two are evaluable.

Question 11Clinical Densitometry Knowledge and Skills

Which precision assessment practice is recommended for a DXA technologist?

  1. Scan 30 patients three times each
  2. Scan 5 patients five times each
  3. Scan 15 patients twice each or 30 patients twice each per ISCD guidance Correct answer.
  4. Scan one phantom daily for a month

Explanation

ISCD recommends a precision assessment using repeat measurements in a sample of patients (commonly 15 patients measured twice, or 30 patients measured twice for the spine) to calculate the LSC. Phantom scans address machine stability, not in vivo precision.

Question 12Clinical Densitometry Knowledge and Skills

A patient's BMD at the total hip is 0.700 g/cm² and the young adult reference mean is 1.000 g/cm² with a standard deviation of 0.100 g/cm². What is the T-score?

  1. -1.0
  2. -7.0
  3. -0.3
  4. -3.0 Correct answer.

Explanation

The T-score equals the measured BMD minus the reference mean, divided by the reference standard deviation: (0.700 - 1.000) / 0.100 = -3.0. This value falls in the osteoporotic range.

Question 13Clinical Densitometry Knowledge and Skills

Which condition makes a lumbar spine DXA result unreliable for diagnosis?

  1. Mild osteoarthritis at L4
  2. Recent lumbar surgery with hardware at L2-L3 Correct answer.
  3. A body mass index of 28
  4. A prior distal radius fracture

Explanation

Metallic hardware produces extreme attenuation and invalidates the spine measurement at affected levels. The hip or forearm should then be used for diagnosis.

Question 14Clinical Densitometry Knowledge and Skills

What is the primary purpose of daily quality-control scanning of a spine phantom?

  1. To determine the appropriate scan mode
  2. To detect scanner drift and stability problems Correct answer.
  3. To calculate the patient's LSC
  4. To establish the young adult reference mean

Explanation

Phantom QC monitors the stability of the densitometer over time and detects drift or malfunction. It does not establish reference data or patient precision.

Question 15Clinical Densitometry Knowledge and Skills

Which patient instruction is most important before a lumbar spine DXA?

  1. Empty the bladder and remove metal objects Correct answer.
  2. Drink two glasses of water
  3. Fast for 12 hours
  4. Avoid all medications for a week

Explanation

Bladder emptying and removal of metal objects such as zippers or buttons reduce artifact and improve measurement accuracy. Routine fasting or medication changes are not required for DXA.

Question 16Clinical Densitometry Knowledge and Skills

A postmenopausal woman has a hip T-score of -2.6 and no prior fracture. What diagnosis does this T-score establish?

  1. Osteoporosis Correct answer.
  2. Secondary hyperparathyroidism
  3. Low bone mass (osteopenia)
  4. Normal bone density

Explanation

A T-score of -2.5 or lower at the hip meets the WHO criterion for osteoporosis regardless of fracture history. Low bone mass corresponds to T-scores between -1.0 and -2.5.

Question 17Clinical Densitometry Knowledge and Skills

Which factor most strongly affects the precision of a lumbar spine DXA measurement?

  1. Patient positioning and vertebral level selection Correct answer.
  2. The color of the display monitor
  3. The time of day of the appointment
  4. The patient's shoe size

Explanation

Consistent positioning and correct identification of vertebral levels are major determinants of spine precision. Inconsistent level selection or rotation increases measurement error.

Question 18Clinical Densitometry Knowledge and Skills

What does a Z-score of -2.2 in a 30-year-old man indicate?

  1. Osteoporosis by WHO criteria
  2. An invalid measurement
  3. BMD below the expected range for age Correct answer.
  4. Normal bone density

Explanation

In men under 50 and premenopausal women, a Z-score of -2.0 or lower is described as below the expected range for age. The WHO T-score classification is not applied in this group.

Question 19Clinical Densitometry Knowledge and Skills

Which hip region of interest is preferred for diagnostic classification?

  1. Intertrochanteric region
  2. Greater trochanter
  3. Ward's triangle
  4. Total hip or femoral neck Correct answer.

Explanation

ISCD recommends using the femoral neck or total hip for diagnosis. Ward's triangle and the greater trochanter are not used for diagnostic classification.

Question 20Clinical Densitometry Knowledge and Skills

A patient's follow-up BMD decreased by 0.020 g/cm², which is less than the LSC. How should this be interpreted?

  1. The change cannot be distinguished from measurement error Correct answer.
  2. The scanner requires recalibration
  3. Significant bone loss has occurred
  4. The patient has developed osteoporosis

Explanation

A change smaller than the LSC falls within the expected range of measurement variability and cannot be considered real. Clinical decisions should not be based on changes below the LSC.

Question 21Clinical Densitometry Knowledge and Skills

Which statement best describes the appropriate use of the forearm DXA in clinical practice?

  1. It is used when hip and spine cannot be measured or interpreted Correct answer.
  2. It is the preferred site for all adults
  3. It is used only in research settings
  4. It replaces hip measurement in older men

Explanation

The one-third radius is a valid diagnostic site when the hip and spine are unavailable or uninterpretable, such as in severe obesity or prior surgery. It is not the preferred site when hip and spine can be measured.

Question 22Clinical Densitometry Knowledge and Skills

A technologist notices that the spine phantom QC values have drifted progressively downward over several weeks. What is the most appropriate first action?

  1. Continue scanning and ignore the trend
  2. Change the reference database
  3. Recalculate the patient's LSC
  4. Investigate the scanner and perform service checks per protocol Correct answer.

Explanation

Progressive drift in phantom values signals a potential equipment problem that requires investigation and service evaluation. Ignoring the trend risks inaccurate patient results.

Question 23Clinical Densitometry Knowledge and Skills

A 70-year-old woman has a spine T-score of -2.7 but severe degenerative changes at L2-L4. The total hip T-score is -2.0. How should the diagnosis be determined?

  1. Average the spine and hip values
  2. Use the hip T-score of -2.0 Correct answer.
  3. Use the spine T-score of -2.7
  4. Report the study as uninterpretable

Explanation

When the spine is invalidated by degenerative change, the diagnosis should be based on the valid hip measurement. A hip T-score of -2.0 indicates low bone mass, not osteoporosis.

Question 24Clinical Densitometry Knowledge and Skills

A 45-year-old premenopausal woman has a spine Z-score of -2.4 and a history of a low-trauma wrist fracture. What is the most appropriate interpretation?

  1. Normal bone density for her age
  2. A measurement error requiring repeat scan
  3. Osteoporosis by T-score criteria
  4. BMD below the expected range for age, warranting further evaluation Correct answer.

Explanation

In premenopausal women, a Z-score of -2.0 or lower indicates BMD below the expected range for age and prompts evaluation for secondary causes. The WHO T-score classification is not applied in this group.

Question 25Clinical Densitometry Knowledge and Skills

A patient's BMD is measured with two different technologists using slightly different positioning, producing a difference of 0.030 g/cm². The LSC is 0.025 g/cm². What does this most likely represent?

  1. True biological change
  2. A need to change diagnostic criteria
  3. A change exceeding the LSC, so it is statistically significant
  4. A precision error that should be documented and addressed Correct answer.

Explanation

Although the difference exceeds the LSC, the involvement of differing positioning between technologists introduces operator-related variability that should be addressed through standardized positioning. Documenting and correcting technique improves future precision.

Question 26Clinical Densitometry Knowledge and Skills

Which skeletal site is measured by DXA to establish the diagnosis of osteoporosis in most postmenopausal women and men over age 50?

  1. Calcaneus by ultrasound
  2. Lumbar spine, total hip, or femoral neck Correct answer.
  3. Whole-body bone mineral content
  4. Distal radius only

Explanation

ISCD guidance supports diagnostic classification using the lumbar spine, total hip, or femoral neck T-score, with the lowest of these sites used when multiple valid sites are available. Peripheral sites such as the forearm are reserved for specific circumstances such as hyperparathyroidism or when central sites cannot be measured.

Question 27Clinical Densitometry Knowledge and Skills

What does the T-score compare in a DXA report?

  1. The patient's BMD with the mean of a young adult reference population of the same sex Correct answer.
  2. The patient's BMD with their own prior measurement
  3. The patient's bone mineral content with their body weight
  4. The patient's BMD with the mean of an age-matched reference population

Explanation

The T-score expresses the number of standard deviations a patient's BMD lies from the mean of a young, sex-matched reference population. The age-matched comparison is instead expressed as the Z-score.

Question 28Clinical Densitometry Knowledge and Skills

Which instruction should be given to a patient scheduled for a DXA scan to avoid a falsely elevated result?

  1. Drink a calcium supplement just before the appointment
  2. Remove any metal objects and avoid recent contrast studies that could interfere Correct answer.
  3. Perform vigorous exercise immediately before the scan
  4. Wear clothing with thick metal buttons over the hip

Explanation

Metal objects and retained contrast material can attenuate the x-ray beam and artifactually raise measured BMD, so they must be removed or the study rescheduled. Recent exercise and calcium intake do not artifactually elevate BMD.

Question 29Clinical Densitometry Knowledge and Skills

What is the primary purpose of a least significant change (LSC) in DXA monitoring?

  1. To define the smallest change between two scans that exceeds measurement error Correct answer.
  2. To set the phantom QC acceptance range
  3. To determine the reference database used for T-scores
  4. To classify a patient as osteoporotic

Explanation

The LSC is derived from precision error and defines the magnitude of change that can be considered real rather than due to measurement variability. Changes smaller than the LSC should not be interpreted as true biological change.

Question 30Clinical Densitometry Knowledge and Skills

Which body-composition assessment is DXA commonly used to provide?

  1. Trabecular bone score
  2. Regional and total fat and lean mass Correct answer.
  3. Bone marrow cellularity
  4. Vertebral fracture grading

Explanation

Whole-body DXA partitions the body into bone mineral, lean, and fat compartments, providing regional and total fat and lean mass estimates. It does not measure marrow cellularity, trabecular microarchitecture, or fracture grade.

Question 31Clinical Densitometry Knowledge and Skills

Which statement correctly describes the Z-score threshold that should prompt additional evaluation in a child or adolescent?

  1. A Z-score of -0.5 or lower
  2. A Z-score of 0.0
  3. A Z-score of -2.0 or lower Correct answer.
  4. A Z-score of +1.0 or higher

Explanation

In children and adolescents, a Z-score at or below -2.0 is considered below the expected range for age and warrants further evaluation for secondary causes. T-scores are not used for diagnosis in this age group.

Question 32Clinical Densitometry Knowledge and Skills

What is the role of the reference database in DXA interpretation?

  1. It sets the radiation dose delivered to the patient
  2. It defines the region-of-interest placement for the hip
  3. It determines the scanning speed of the densitometer
  4. It supplies the normative mean and standard deviation used to compute T-scores and Z-scores Correct answer.

Explanation

Reference databases provide the normative values against which a patient's BMD is compared to generate T-scores and Z-scores. Scanner speed, dose, and ROI placement are determined by acquisition and analysis protocols, not by the reference database.

Question 33Clinical Densitometry Knowledge and Skills

Which skeletal site is typically measured when the hip and spine cannot be evaluated and a central DXA is still desired?

  1. Sacroiliac joint
  2. Calcaneus
  3. Whole body
  4. Distal one-third radius Correct answer.

Explanation

The distal one-third radius is the standard peripheral DXA site used when hip and spine measurements are not feasible or valid. It provides a validated site for diagnostic classification in defined circumstances.

Question 34Clinical Densitometry Knowledge and Skills

A technologist performs duplicate spine scans on 15 patients to calculate precision. What is the standard summary statistic reported for in vivo precision?

  1. Pearson correlation between the two scans
  2. Median BMD in g/cm²
  3. Root-mean-square standard deviation expressed as a coefficient of variation Correct answer.
  4. Mean T-score difference between scans

Explanation

In vivo precision is expressed as the root-mean-square standard deviation, usually converted to a coefficient of variation in percent. Correlation between paired scans does not capture measurement error.

Question 35Clinical Densitometry Knowledge and Skills

A 68-year-old man has a total hip T-score of -1.8 and a femoral neck T-score of -2.6. Which value should be used for diagnostic classification?

  1. The total hip T-score of -1.8
  2. The higher of the two T-scores
  3. The average of the two T-scores
  4. The femoral neck T-score of -2.6 Correct answer.

Explanation

When multiple valid sites are measured, the lowest T-score among the diagnostic sites is used for classification. The femoral neck value of -2.6 therefore governs the diagnosis.

Question 36Clinical Densitometry Knowledge and Skills

A patient's spine BMD is 0.850 g/cm² and the young adult reference mean is 1.000 g/cm² with a standard deviation of 0.100 g/cm². What is the T-score?

  1. -1.5 Correct answer.
  2. -2.5
  3. +1.5
  4. -0.15

Explanation

The T-score equals the difference between the patient value and the reference mean divided by the reference standard deviation: (0.850 - 1.000) / 0.100 = -1.5.

Question 37Clinical Densitometry Knowledge and Skills

A 55-year-old postmenopausal woman has a lumbar spine T-score of -2.8 with no fragility fracture. What does this T-score establish?

  1. Osteoporosis by densitometric criteria Correct answer.
  2. Osteopenia
  3. Established severe osteoporosis
  4. Normal bone density

Explanation

A T-score of -2.5 or lower at a diagnostic site meets the densitometric definition of osteoporosis in a postmenopausal woman. Severe or established osteoporosis additionally requires one or more fragility fractures.

Question 38Clinical Densitometry Knowledge and Skills

A 30-year-old woman has a lumbar spine Z-score of -2.6. What is the most appropriate interpretation?

  1. Bone density is below the expected range for age and warrants evaluation for secondary causes Correct answer.
  2. The result indicates a laboratory error and should be repeated without further action
  3. The result is normal for a woman of this age
  4. The result is diagnostic of postmenopausal osteoporosis

Explanation

In premenopausal women and men under 50, the Z-score rather than the T-score is used, and a value of -2.0 or lower is below the expected range for age. Such a finding should prompt investigation for secondary causes of bone loss.

Question 39Clinical Densitometry Knowledge and Skills

A spine DXA scan shows a markedly elevated BMD at L4 only, and the patient reports recent barium studies. What is the most appropriate action?

  1. Report the elevated value as a true increase in bone density
  2. Repeat the scan immediately in the same session
  3. Exclude the affected vertebra from analysis and document the artifact Correct answer.
  4. Average all vertebrae including the affected one

Explanation

Retained contrast material can artifactually raise BMD at an isolated vertebra, so affected levels should be excluded from analysis and the reason documented. Repeating the scan in the same session would not remove retained contrast.

Question 40Clinical Densitometry Knowledge and Skills

Which hip region of interest is generally preferred for monitoring BMD change over time?

  1. Total hip Correct answer.
  2. Greater trochanter
  3. Femoral shaft
  4. Ward's triangle

Explanation

The total hip region has the best reproducibility among hip regions and is preferred for longitudinal monitoring. Ward's triangle is highly variable and is not recommended for monitoring.

Question 41Clinical Densitometry Knowledge and Skills

A patient's follow-up total hip BMD is 0.020 g/cm² lower than the prior study, and the LSC for that site is 0.030 g/cm². How should this be interpreted?

  1. The patient has developed osteoporosis
  2. The change is within measurement error and is not significant Correct answer.
  3. The prior scan must have been performed incorrectly
  4. The change represents definite bone loss

Explanation

A change smaller than the least significant change cannot be distinguished from measurement variability and should not be interpreted as real. Only changes exceeding the LSC are considered significant.

Question 42Clinical Densitometry Knowledge and Skills

Which patient factor most limits the diagnostic usefulness of a lumbar spine DXA in an older adult?

  1. A body mass index of 24 kg/m²
  2. Mild scoliosis that does not alter positioning
  3. Recent mild physical activity
  4. Extensive degenerative osteophytosis and aortic calcification Correct answer.

Explanation

Degenerative changes and aortic calcification add density to the measured region and artifactually raise spine BMD, reducing diagnostic accuracy. In such cases the hip or forearm may provide more reliable information.

Question 43Clinical Densitometry Knowledge and Skills

A 70-year-old woman has a femoral neck T-score of -2.5 and reports a low-trauma hip fracture two years ago. What is the correct classification?

  1. Osteopenia
  2. Severe or established osteoporosis Correct answer.
  3. Secondary osteoporosis only
  4. Normal bone density

Explanation

A T-score of -2.5 or lower accompanied by one or more fragility fractures meets the criteria for severe or established osteoporosis. The fracture history distinguishes this from uncomplicated osteoporosis.

Question 44Clinical Densitometry Knowledge and Skills

Which statement best describes the appropriate use of vertebral fracture assessment (VFA) with DXA?

  1. It is used only in children under age 10
  2. It identifies prevalent vertebral deformities that influence fracture risk assessment Correct answer.
  3. It replaces BMD measurement for diagnosing osteoporosis
  4. It measures trabecular microarchitecture directly

Explanation

VFA uses lateral spine imaging acquired on the densitometer to detect vertebral deformities, which add prognostic information beyond BMD. It does not replace BMD measurement or directly assess microarchitecture.

Question 45Clinical Densitometry Knowledge and Skills

A patient's BMD is measured on two different DXA systems from different manufacturers. Why should the results not be directly compared?

  1. Only one manufacturer is approved for clinical use
  2. Different manufacturers use different calibration and reference databases Correct answer.
  3. The patient's bone density changes between systems
  4. BMD values are identical across all systems

Explanation

Cross-calibration differences and manufacturer-specific reference databases mean BMD values from different systems are not directly interchangeable. Longitudinal monitoring should ideally use the same system.

Question 46Clinical Densitometry Knowledge and Skills

What is the primary reason for performing an in vivo precision assessment on each technologist?

  1. To select the appropriate T-score threshold
  2. To determine the scanner's radiation dose
  3. To validate the reference database
  4. To establish that technologist's precision error and the LSC used for monitoring Correct answer.

Explanation

Precision is technologist- and site-specific, so each technologist should establish their own precision error to calculate a valid LSC. This ensures that changes over time can be interpreted correctly.

Question 47Clinical Densitometry Knowledge and Skills

A 62-year-old woman has a lumbar spine T-score of -2.7 but the scan is limited by severe degenerative changes at L2-L4. Her total hip T-score is -2.0. How should the diagnosis be determined?

  1. Repeat the spine scan until the artifact resolves
  2. Use the spine T-score and diagnose osteoporosis
  3. Average the spine and hip T-scores
  4. Use the total hip T-score, since the spine is unreliable, and classify as osteopenia Correct answer.

Explanation

When the spine measurement is invalidated by degenerative artifact, the hip should be used for classification. A total hip T-score of -2.0 falls in the osteopenia range, so osteoporosis is not diagnosed on these data.

Question 48Clinical Densitometry Knowledge and Skills

A 45-year-old premenopausal woman has a lumbar spine Z-score of -2.4 and a history of a low-trauma wrist fracture. Which statement best reflects ISCD-based interpretation?

  1. The result meets the densitometric definition of osteoporosis
  2. The result is normal for a premenopausal woman
  3. The Z-score is below the expected range for age and secondary causes should be investigated Correct answer.
  4. The fracture is unrelated to bone density and requires no further evaluation

Explanation

In premenopausal women, the Z-score is used, and a value of -2.0 or lower is below the expected range for age, prompting evaluation for secondary causes. A fragility fracture in this context also warrants clinical attention rather than dismissal.

Question 49Clinical Densitometry Knowledge and Skills

A technologist notices that spine phantom QC values have gradually decreased over several weeks while remaining within the manufacturer's range. What is the most appropriate action?

  1. Continue scanning without comment because values remain within range
  2. Change the reference database to match the new values
  3. Immediately repeat all patient scans from the past year
  4. Investigate for a systematic cause such as calibration drift or scanner maintenance needs Correct answer.

Explanation

A consistent trend, even within acceptance limits, suggests systematic drift and should prompt investigation of calibration, hardware, or software issues. Trending QC values is a key purpose of the phantom program.

Question 50Clinical Densitometry Knowledge and Skills

Which statement best explains why the forearm measurement is useful in a patient with primary hyperparathyroidism?

  1. The forearm is measured because it has no reference database
  2. The distal one-third radius is rich in cortical bone and reflects the cortical bone loss typical of hyperparathyroidism Correct answer.
  3. The forearm measurement replaces the need for hip and spine scanning
  4. The forearm is measured because it is the only site unaffected by body weight

Explanation

Hyperparathyroidism preferentially affects cortical bone, and the distal one-third radius is predominantly cortical, making it a sensitive site in this condition. This is one of the defined indications for forearm measurement.