Quantitative Sensory Testing (QST): Difference between revisions

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== Introduction ==
== Introduction ==
Quantitative sensory testing (QST) is a systematic psychophysical test method used to measure sensory thresholds for pain, touch, vibration, and temperature sensations.<ref name=":0">Horowitz SH. Neuropathic pain: is the emperor wearing clothes. Current Therapy in Pain, WB Saunders. 2009:9-14.</ref>It quantifies individual sensory perceptions using direct patient feedback. It tests for sensory loss (hypoesthesia, hypoalgesia) and sensory gain (hyperesthesia, hyperalgesia, allodynia)<ref name=":2">Weaver KR, Griffioen MA, Klinedinst NJ, Galik E, Duarte AC, Colloca L, Resnick B, Dorsey SG, Renn CL. [[Quantitative sensory testing across chronic pain conditions and use in special populations.]] Frontiers in Pain Research. 2022 Jan 28;2:779068.</ref>. Sophisticated computerised equipment is often used in clinical trials, but hand-held tools are also available for clinical use<ref name=":0" />.
Quantitative sensory testing (QST) is a systematic psychophysical test method used to measure sensory thresholds for pain, touch, vibration, and temperature sensations.<ref name=":0">Horowitz SH. Neuropathic pain: is the emperor wearing clothes. Current Therapy in Pain, WB Saunders. 2009:9-14.</ref>It quantifies individual sensory perceptions using direct patient feedback. It tests for sensory loss (hypoesthesia, hypoalgesia) and sensory gain (hyperesthesia, hyperalgesia, allodynia)<ref name=":2">Weaver KR, Griffioen MA, Klinedinst NJ, Galik E, Duarte AC, Colloca L, Resnick B, Dorsey SG, Renn CL. [[Quantitative sensory testing across chronic pain conditions and use in special populations.]] Frontiers in Pain Research. 2022 Jan 28;2:779068.</ref>. The procedure tests nociceptive and non-nociceptive properties of different afferent nerve fibres and central pathways<ref name=":1" />.


== Clinical Application ==
== Clinical Application ==
QST can be used to evaluate any condition that affects sensory function - it may help with diagnosis and disease monitoring. QST can be very useful to identify underlying contributing [[Pain Mechanisms|pain mechanisms]] and pathophysiology, which can assist with targeted intervention strategies<ref name=":2" /><ref name=":1">Mucke M, Cuhls H, Radbruch L, Baron R, Maier C, Tolle T, Treede RD, Rolke R. Quantitative sensory testing (QST). English version. Schmerz. 2016;35:153-60.</ref>. It is best to compare results with normative values, and it is best conducted early after onset of a condition.  
QST can be used to evaluate any condition that affects sensory function - it may help with diagnosis and disease monitoring. QST can be very useful to identify underlying contributing [[Pain Mechanisms|pain mechanisms]] and pathophysiology, which can assist with targeted intervention strategies<ref name=":2" /><ref name=":1">Mucke M, Cuhls H, Radbruch L, Baron R, Maier C, Tolle T, Treede RD, Rolke R. Quantitative sensory testing (QST). English version. Schmerz. 2016;35:153-60.</ref>. It is best to compare results with normative values, and it is best conducted early after onset of a condition - the reason for this is that people with central sensitisation will present with widespread QST abnormalities, rendering the contralateral side an inaccurate comparison site. In early onset cases, the contralateral side is more likely to still reflect the patient's norm, but if predisposing existing sensory abnormalities are present it could interfere with interpretation.  


'''Conditions''' for which QST can be useful include<ref name=":2" /><ref name=":1" />:
'''Conditions''' for which QST can be useful include<ref name=":2" /><ref name=":1" />:
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* [[Knee Osteoarthritis|Knee osteoarthritis]]
* [[Knee Osteoarthritis|Knee osteoarthritis]]


=== Procedure and Components ===
== Procedure ==
Sophisticated computerised equipment is often used in clinical trials, but hand-held tools are also available for clinical use<ref name=":0" />. The following table presents the standardise procedure as recommended by the German Research Network on Neuropathic Pain. Simplified versions will be discussed later:
{| class="wikitable"
|+QST Standardised Procedure <ref name=":1" />
!Test
!Equipment
!Nerves tested
!Instructions
!Measurement
|-
|'''Thermal Testing'''
|Thermode with element and cooling water system
|A-delta fibres and C-fibres
|Thermode is placed on the skin and measure heat and pain/ cold and pain detection between 0 and 50 degrees Celsius
|Average of three consecutive measures
|-
|'''Mechanical Detection'''
|Von Frey Filaments
|A-beta fibres
|Contact with skin for 2 seconds determine at what point the patient detects tactile input
|Average of five above and below-threshold stimulus intensities
|-
|'''Mechanical pain threshold'''
|Needle stimulators
|
|Needle applied perpendicular to the skin in ascending and descending stimulus intensity with skin contact time of 1-2s
|Average of five above and below-threshold stimulus intensities
|-
|'''Mechanical pain sensitivity'''
|Needle stimulators, Q-tip, soft brush, cotton pad
|Allodynia
|Gentle stimuli applied to the 2cm of skin (stroking) with the various instruments
|Subjects are asked to rate the perception of the stimulus using a pain scale of 0-100
|-
|'''Vibration detection threshold'''
|
|
|
|
|-
|'''Pressure pain threshold'''
|
|
|
|
|-
|'''Temporal Summation'''
|
|Wind-up phenomenon
|
|
|}
 
=== Normal values ===
 
=== Components ===
To perform QST, a patient is stimulated with quantified sensory stimuli and based on patient feedback, perception thresholds are identified for the following sensory functions: light touch, pressure, vibration, thermal sensations, heat and cold pain. This way A-delta fibres (small diameter myelinated) and C-fibres (unmyelinated) are assessed.
To perform QST, a patient is stimulated with quantified sensory stimuli and based on patient feedback, perception thresholds are identified for the following sensory functions: light touch, pressure, vibration, thermal sensations, heat and cold pain. This way A-delta fibres (small diameter myelinated) and C-fibres (unmyelinated) are assessed.


* '''Vibration'''
* '''Vibration'''
* '''Cold'''
* '''Cold'''
* Heat
*
*


=== Interpretation ===
=== Bed-side testing ===
 
=== Complementary Tests ===
 
* '''Temporal summation (TS):''' Apply rapidly repeated mechanical stimuli (for 5-10s) to a painful region - if TS is present it will result in an increased pain perception indicating central sensitisation<ref name=":2" />.
* '''[[Weber Two-Point Discrimination Test|2-point discrimination]]:''' Especially useful in upper limb to test tactile perception. Can be impaired in both PNS and CNS conditions. In the absence of peripheral pathology, it could indicate cortical changes in the homunculus.
* '''Conditional pain modulation test (CPM):''' CPM tests the function of central pain inhibition/facilitation. Involves applying a noxious stimulus (thermal or mechanical) to a region remote from the painful site - if descending inhibitory control is functioning properly, the initial source of pain will be less intense during the application of the remote stimulus. <ref name=":2" />*****
 
== Interpretation ==
The table below summarises the link between underlying pain mechanisms / pathophysiology and specific QST findings:
{| class="wikitable"
{| class="wikitable"
|+Meaning of QST results<ref name=":0" /><ref name=":2" />
|+'''Interpretation of QST results: Mechanisms'''<ref name=":0" /><ref name=":2" /><ref name=":1" />
!'''Underlying mechanism'''
!'''Underlying mechanism/ Sign'''
!'''QST finding'''
!'''QST finding'''
|-
|-
|Hypoesthesia (sensory loss)
|''Hypoesthesia (sensory loss)''
|Elevated sensory thresholds
|Elevated sensory thresholds, i.e. decreased sensitivity to non-noxious stimuli
|-
|''Hypoalgesia''
|Elevated sensory thresholds, i.e. decreased sensitivity to noxious stimuli
|-
|-
|Allodynia and hyperalgesia
|''Hyperalgesia''
|Lowered sensory thresholds
|Increased sensitivity (lowered thresholds) to heat, cold, pinprick or deep pressure
|-
|-
|Peripheral sensitisation
|''Allodynia''
|Pain in response to non-noxious stimuli on skin
|-
|''Peripheral sensitisation''
|Heat hyperalgesia (lowered hot pain threshold)
|Heat hyperalgesia (lowered hot pain threshold)
Lowered pain thresholds for pressure/pin prick proximal to painful area or along nerve distribution / segmental region
|-
|-
|Central sensitisation
|''Central sensitisation''
|Static mechanical hyperalgesia or dynamic mechanical allodynia; temporal summation (repeated mechanical and thermal stimuli causes increased pain)
|Increased sensitivity to cold/pin prick/pressure/cold hyperalgesia that is widespread and contralateral; Mechanical allodynia; Temporal summation (repeated mechanical and thermal stimuli causes increased pain)
|-
|-
|Polyneuropathy
|''Polyneuropathy''
|All thresholds elevated
|All thresholds elevated
|-
|-
|Small fibre neuropathy
|''Small fibre neuropathy''
|Vibration thresholds are normal, but others elevated
|Vibration thresholds are normal, but others elevated
|-
|''Nerve deafferation''
|Reduced sensitivity with all tests
|}
|}


=== Limitations ===
* QST abnormalities are present in non neuropathic pain, making it difficult to use QST as a definitive tool for identifying neuropathic pain<ref name=":0" />
* Abnormal findings are not specific for peripheral nerve dysfunction, as central nervous system disorders will also alter sensory thresholds<ref name=":0" />
* It is a subjective psychophysical test, entirely dependent on patient alertness, motivation and willingness to supply accurate feedback. There is large intra- and interindividual variation<ref name=":0" />
=== Complementary Tests ===
Temporal summation
Apply rapidly repeated mechanical stimuli to a painful region - if TS is present it will result in an increased pain perception indicating central sensitisation<ref name=":2" />
'''2-point discrimination'''
'''Conditional pain modulation test (CPM)'''
CPM tests the function of central pain inhibition. Involves applying a noxious stimulus (thermal or mechanical) to a region remote from the painful site - if descending inhibitory control is functioning properly, the initial source of pain will be less intense during the application of the remote stimulus. <ref name=":2" />*****


== Specific Conditions ==
The table below summarises QST findings for specific conditions, as identified in research studies<ref name=":2" />:
The table below summarises QST findings for specific conditions, as identified in research studies<ref name=":2" />:
{| class="wikitable"
{| class="wikitable"
|+
|+'''Common QST results: Conditions'''
!'''Condition'''
!'''Condition'''
!'''QST findings'''
!'''QST findings'''
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|-
|-
|''Chronic low back pain''
|''Chronic low back pain''
|Increased sensitivity (decreased threshold) to heat and pressure; Temporal summation
|(1) Increased sensitivity (decreased threshold) to heat and pressure
|Identifies peripheral and central sensitisation (TS present) components  
(2) Temporal summation
|(1) Indicates peripheral sensitiasation
(2) Central sensitisation components present
|-
|-
|''Lower limb fractures''
|''Lower limb fractures''
|Decreased sensitivity (elevated threshold) to touch and warmth
|Decreased sensitivity (elevated threshold) to touch and increased sensitivity (decreased threshold) to warmth  
|Peripheral nerve injury which can affect limb function and balance
|Identified underlying peripheral nerve injury which can affect limb function and balance
|-
|-
|''Knee OA''
|''Knee OA''
|Increased sensitivity (lowered pressure/cold pain thresholds); Temporal summation (TS)
|(1) Increased sensitivity (lowered   thresholds) to pressure around the knee
|Identifies peripheral and central sensitisation (distal sites affected and TS) components if present and can predict surgery outcomes
(2) Increased sensitivity to pressure and cold at distal sites; Temporal summation (TS with pinprick
|(1) Indicates peripheral sensitisation  
(2) Indicates central sensitisation - predicts poor surgery outcomes if not addressed; will likely not respond fully to NSAIDs
|-
|''CRPS''
|
|
|}
|}


 
== Limitations ==
[[File:QST.jpg|frameless|600x600px]]
* QST abnormalities are present in non neuropathic pain, making it difficult to use QST as a definitive tool for identifying neuropathic pain<ref name=":0" />
* Abnormal findings are not specific for peripheral nerve dysfunction, as central nervous system disorders will also alter sensory thresholds<ref name=":0" />
* It is a subjective psychophysical test, entirely dependent on patient alertness, motivation and willingness to supply accurate feedback. There is large intra- and interindividual variation<ref name=":0" />


== Summary ==
== Summary ==

Revision as of 10:08, 23 August 2023

This article or area is currently under construction and may only be partially complete. Please come back soon to see the finished work! (23/08/2023)

Original Editor - Melissa Coetsee

Top Contributors - Melissa Coetsee and Carina Therese Magtibay  

Introduction[edit | edit source]

Quantitative sensory testing (QST) is a systematic psychophysical test method used to measure sensory thresholds for pain, touch, vibration, and temperature sensations.[1]It quantifies individual sensory perceptions using direct patient feedback. It tests for sensory loss (hypoesthesia, hypoalgesia) and sensory gain (hyperesthesia, hyperalgesia, allodynia)[2]. The procedure tests nociceptive and non-nociceptive properties of different afferent nerve fibres and central pathways[3].

Clinical Application[edit | edit source]

QST can be used to evaluate any condition that affects sensory function - it may help with diagnosis and disease monitoring. QST can be very useful to identify underlying contributing pain mechanisms and pathophysiology, which can assist with targeted intervention strategies[2][3]. It is best to compare results with normative values, and it is best conducted early after onset of a condition - the reason for this is that people with central sensitisation will present with widespread QST abnormalities, rendering the contralateral side an inaccurate comparison site. In early onset cases, the contralateral side is more likely to still reflect the patient's norm, but if predisposing existing sensory abnormalities are present it could interfere with interpretation.

Conditions for which QST can be useful include[2][3]:

Procedure[edit | edit source]

Sophisticated computerised equipment is often used in clinical trials, but hand-held tools are also available for clinical use[1]. The following table presents the standardise procedure as recommended by the German Research Network on Neuropathic Pain. Simplified versions will be discussed later:

QST Standardised Procedure [3]
Test Equipment Nerves tested Instructions Measurement
Thermal Testing Thermode with element and cooling water system A-delta fibres and C-fibres Thermode is placed on the skin and measure heat and pain/ cold and pain detection between 0 and 50 degrees Celsius Average of three consecutive measures
Mechanical Detection Von Frey Filaments A-beta fibres Contact with skin for 2 seconds determine at what point the patient detects tactile input Average of five above and below-threshold stimulus intensities
Mechanical pain threshold Needle stimulators Needle applied perpendicular to the skin in ascending and descending stimulus intensity with skin contact time of 1-2s Average of five above and below-threshold stimulus intensities
Mechanical pain sensitivity Needle stimulators, Q-tip, soft brush, cotton pad Allodynia Gentle stimuli applied to the 2cm of skin (stroking) with the various instruments Subjects are asked to rate the perception of the stimulus using a pain scale of 0-100
Vibration detection threshold
Pressure pain threshold
Temporal Summation Wind-up phenomenon

Normal values[edit | edit source]

Components[edit | edit source]

To perform QST, a patient is stimulated with quantified sensory stimuli and based on patient feedback, perception thresholds are identified for the following sensory functions: light touch, pressure, vibration, thermal sensations, heat and cold pain. This way A-delta fibres (small diameter myelinated) and C-fibres (unmyelinated) are assessed.

  • Vibration
  • Cold

Bed-side testing[edit | edit source]

Complementary Tests[edit | edit source]

  • Temporal summation (TS): Apply rapidly repeated mechanical stimuli (for 5-10s) to a painful region - if TS is present it will result in an increased pain perception indicating central sensitisation[2].
  • 2-point discrimination: Especially useful in upper limb to test tactile perception. Can be impaired in both PNS and CNS conditions. In the absence of peripheral pathology, it could indicate cortical changes in the homunculus.
  • Conditional pain modulation test (CPM): CPM tests the function of central pain inhibition/facilitation. Involves applying a noxious stimulus (thermal or mechanical) to a region remote from the painful site - if descending inhibitory control is functioning properly, the initial source of pain will be less intense during the application of the remote stimulus. [2]*****

Interpretation[edit | edit source]

The table below summarises the link between underlying pain mechanisms / pathophysiology and specific QST findings:

Interpretation of QST results: Mechanisms[1][2][3]
Underlying mechanism/ Sign QST finding
Hypoesthesia (sensory loss) Elevated sensory thresholds, i.e. decreased sensitivity to non-noxious stimuli
Hypoalgesia Elevated sensory thresholds, i.e. decreased sensitivity to noxious stimuli
Hyperalgesia Increased sensitivity (lowered thresholds) to heat, cold, pinprick or deep pressure
Allodynia Pain in response to non-noxious stimuli on skin
Peripheral sensitisation Heat hyperalgesia (lowered hot pain threshold)

Lowered pain thresholds for pressure/pin prick proximal to painful area or along nerve distribution / segmental region

Central sensitisation Increased sensitivity to cold/pin prick/pressure/cold hyperalgesia that is widespread and contralateral; Mechanical allodynia; Temporal summation (repeated mechanical and thermal stimuli causes increased pain)
Polyneuropathy All thresholds elevated
Small fibre neuropathy Vibration thresholds are normal, but others elevated
Nerve deafferation Reduced sensitivity with all tests


The table below summarises QST findings for specific conditions, as identified in research studies[2]:

Common QST results: Conditions
Condition QST findings Implication
Chronic low back pain (1) Increased sensitivity (decreased threshold) to heat and pressure

(2) Temporal summation

(1) Indicates peripheral sensitiasation

(2) Central sensitisation components present

Lower limb fractures Decreased sensitivity (elevated threshold) to touch and increased sensitivity (decreased threshold) to warmth Identified underlying peripheral nerve injury which can affect limb function and balance
Knee OA (1) Increased sensitivity (lowered thresholds) to pressure around the knee

(2) Increased sensitivity to pressure and cold at distal sites; Temporal summation (TS with pinprick

(1) Indicates peripheral sensitisation

(2) Indicates central sensitisation - predicts poor surgery outcomes if not addressed; will likely not respond fully to NSAIDs

CRPS

Limitations[edit | edit source]

  • QST abnormalities are present in non neuropathic pain, making it difficult to use QST as a definitive tool for identifying neuropathic pain[1]
  • Abnormal findings are not specific for peripheral nerve dysfunction, as central nervous system disorders will also alter sensory thresholds[1]
  • It is a subjective psychophysical test, entirely dependent on patient alertness, motivation and willingness to supply accurate feedback. There is large intra- and interindividual variation[1]

Summary[edit | edit source]

QST can be a very valuable clinical tool in patients with chronic pain by assisting to characterise pain experiences. It provides information about potential underlying mechanisms contributing to pain, therefore incorporating QST may improve the ability to implement individualised treatment plans based on underlying mechanisms[2].

Resources[edit | edit source]

or

  1. numbered list
  2. x

References[edit | edit source]

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 Horowitz SH. Neuropathic pain: is the emperor wearing clothes. Current Therapy in Pain, WB Saunders. 2009:9-14.
  2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 Weaver KR, Griffioen MA, Klinedinst NJ, Galik E, Duarte AC, Colloca L, Resnick B, Dorsey SG, Renn CL. Quantitative sensory testing across chronic pain conditions and use in special populations. Frontiers in Pain Research. 2022 Jan 28;2:779068.
  3. ↑ 3.0 3.1 3.2 3.3 3.4 Mucke M, Cuhls H, Radbruch L, Baron R, Maier C, Tolle T, Treede RD, Rolke R. Quantitative sensory testing (QST). English version. Schmerz. 2016;35:153-60.
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