Week 6: Rheumatology (3) (investigations) Flashcards
1
Q
Investigations in rheumatology
A
- Bloods (FBC, U and E, uric acid, LFTs, CK
- Inflammatory markers (ESR, PV, CRP)
- Human leukocyte antigen B25 (HLA_B27)
- Urinalysis
- Synovial fluid analysis
- Biopsy
- NCS and EMG
- X-ray
- US
- MRI
2
Q
interpreting blood results: Hb
A
- Anaemia of chronic disease most common in RA, Fe deficiency may be due to NSAIDs
3
Q
interpreting blood results: platelets
A
- Rise with
- inflammation or bleeding
- Fall in SLE
4
Q
interpreting blood results neutrophils
A
- Rise with
- inflammation, sepsis and prednisolone usage;
- Fall in SLE or with DMARD toxicity
5
Q
interpreting blood results: lymphocytes
A
- Falls in
- SLE or DMARD induced
6
Q
interpreting blood results: U and E
A
- Rise due to
- NSAIDs
- renal disease in lupus/vasculitis or gout
7
Q
interpreting blood results: uric acid
A
- rise in gout
- fall with inflammation
8
Q
interpreting blood results: LFTs
A
- Rise due to Hepatitis due to DMARD toxicity
9
Q
interpreting blood results: CK, ALT, LDH
A
- Rise in myositis
10
Q
inflammatory markers
A
ERS
PV
CRP
11
Q
ESR
A
- Erythrocyte sedimentation rate
- Reference range men <50 yrs (<5mm/h); women < 50 yrs, (<7mm/h) ; rises in pregnancy ;both sexes> 50 yrs (<30mm/h)
- Test reflects presence of: fibrinogen and immunoglobulins
- Effect of anaemia- rises
- Advantages
- Widely understood
- Well established in diagnosis and monitoring of GCA
- Disad
- No technique for calibration to test for accuracy
- Poor reproducibility
- Test takes 2 hour
- Must be carried out within 4 hours of blood sampling
12
Q
PV
A
- Plasma viscosity
- Reference range independent of age & sex (1.5-1.72 mPa)
- Test reflects presence of: fibrinogen and immunoglobulins
- Anaemia has no effect
- Advantages
- Automatable
- Sensitive
- Not affected by haematocrit
- Measurement can eb made on stored sample
- Disadvantages
- Not widely used- lack of familiarity with interpretation
13
Q
CRP
A
- C-reactive protein
- Reference range variable but constant within individuals (<10 mg/L)
- Anaemia has no effect
- Advantages
- Automatable
- Very sensitive
- Not affected by haematocrit
- Measurement can be made on stored blood samples
- Disad
- Short lived indicator
- Good at monitoring sepsis as rises and falls quickly
- Short lived indicator
14
Q
autoantibodies found in RA
A
RF and anti-CCP
15
Q
autoantibodies found in OA
A
N/A
16
Q
autoantibodies found in Sjogrens
A
Anti- Ro and Anti-La
RF and anti ds-DNA
17
Q
auotantibodies found in SLE
A
ANA
Anti-dsDNA
Anti-Ro, Anti-La
Raised ESR or PV
decreased:
- C3 and C4 decrease with disease activity
18
Q
autoantibodies found in polymyalgia rheumatica
A
Raised ESR or CRP
19
Q
autoantibodies found in spondyloarthropathies
A
HLA-B27 gene
- Ankylosing spondylitis- raised CRP
- Psoriatic arthritis- CRP raised
- Reactive arthritis- CRP raised
20
Q
autoantibodies found in raynauds
A
Associated with scleroderma, SLE, dermatomyositis and polymyositis, Sjoren’
21
Q
autoantibodies found in vasculitis
A
ANA, ANCA, RF
C3, C4
22
Q
autoantibodies found in systemic sclerosis (SSc)
A
ANA
Anti-centromere- limited SSc
Scl-70 (topoisomerase) and antiRNA polymerase III- diffuse SSc
23
Q
autoantibodies found in polymycositis
A
Anti-Jo1
24
Q
Human leukocyte antigen B27 (HLA-B27)
A
- HLA-B27 is a class 1 surface antigen. It is found in around 10% of white people. Its prevalence varies with ethnicity.
- It is strongly associated with ankylosing spondylitis, iritis and juvenile arthritis.
- Around 90% of white people with AS are positive for this.
25
**Urinalysis**
Renal disease may first be detected by the presence of protein and/or blood on a urine dipstick. This test is mandated in SLE and vasculitis.
26
**Synovial fluid analysis**
* This is the most important investigation in suspected cases of septic arthritis and crystal arthropathy.
* Send immediately for gram stain and culture, before antibiotic treatment if possible.
* Polarized light microscopy may reveal negatively birefringent needle shaped crystals in gout or **positively** **birefringent rhomboid shaped crystals** in pseudo gout.
27
**Biopsy**
* Temporal artery biopsy is the most common biopsy requested by rheumatologists. However, due to the patchy nature of vascultis in GCA false negatives may occur.
* Muscle biopsy for polymyositis or dermatomyositis
* Skin biopsy is useful in vasculitis, dermatomyositis and SLE
* Lip/salivary gland biopsy for Sjogren's
* Lymph node biopsy may be needed in SLE to rule out lymphoma or TB
* Synovial biopsy may be needed for rare tumours or infections
* Sural nerve biopsy uncommonly requested but helpful in vasculitis with mononeuritis multiplex/periph neuropathy Renal biopsy for vasculitis, SLE
28
**NCS (nerve conduction studies) & EMG (electromyography**)
* NCS help to confirm peripheral nerve entrapment e.g. carpal tunnel syndrome.
* EMG records spontaneous and voluntary muscle activity and has characteristic abnormalities in myositis.
29
**X-ray**
The least expensive and most easily available initial investigation. Avoid unnecessary x-rays to minimize radiation risk. Good for assessing bone. Often normal in inflammatory arthritis for up to 5 years after diagnosis. Reflects damage rather than any ongoing disease activity.
30
RA X-ray
* (LESS) - think MCJ
* Loss of joint space
* Erosions
* Soft tissue swelling
* Subluxation
31
OA X-ray
* Joint space narrowing
* Subarticular sclerosis
* Bone cyst
* Osteophytes
32
**Ultrasound**
Used mainly for diagnosis of early synovitis and erosions in early RA and PsA. Good for soft tissue structures like bursae and tendons. May be used to guide joint injections and soft tissue injections such as for tenosynovitis. Simple, portable & cheap. Very operator dependent. Difficult to independently review images obtained.
33
**Magnetic resonance imaging (MRI)**
Expensive but good for identification of early inflammation especially in spondyloarthritis. Highly reproducible. Very good for knee and shoulder – to look for meniscal and ligament tears and rotator cuff tears. Useful in cases of suspected infection or neoplasia. Also used for investigation of myositis. Contraindications are: claustrophobia/pacemaker/metal body in eye/surgical clips in brain.
34
**Dual energy X-ray absorptiometry (DEXA)**
Radiation dose about 1/10 of CXR dose.
Evaluation for osteoporosis. Estimates bone mineral density at different sites i.e hip, spine and forearm. T score indicates BMD of the patient compared to a normal person of same age and sex.
***Osteoporosis is diagnosed when the T score is less than 2.5 standard deviations below the mean.***
