Guillain-Barre syndrome (GBS)
Abstracted from authoritative source:
Overview: Guillain-Barre syndrome (GBS) is a rare but serious post-infectious immune-mediated neuropathy. It results from the autoimmune destruction of nerves in the peripheral nervous system causing symptoms such as numbness, tingling, and weakness that can progress to paralysis. Guillain-Barre syndrome (GBS) is the most common cause of acute, flaccid, neuromuscular paralysis in the United States. Many infections have been linked with GBS. The most common are gastrointestinal or respiratory illnesses. Up to 70% of patients have reported an antecedent illness in the 1 to 6 weeks before the presentation of GBS. rare, with an incidence of 0.4 to 2 per 100,000. Miller Fisher syndrome (MFS) is a considered a variant of GBS, characterized by ophthalmoplegia, ataxia, and areflexia.
Presentation: Guillain-Barre syndrome (GBS) patients describe a fulminant course of symptoms that usually include ascending weakness and non-length dependent sensory symptoms. Required features - progressive weakness of legs and arms, trunk, bulbar and facial muscles, and external ophthalmoplegia; areflexia or decreased reflexes in weak limbs. By definition, the nadir is usually reached within 4 weeks. Symmetric involvement is a key feature of GBS. GBS is usually considered monophasic; therefore, a relapsing or remitting course at presentation would be considered atypical. Additionally, a prior GBS event (recurrent GBS) is also unusual, occurring in < 10% of all patients.
Diagnostics Evaluation: Guillain-Barre syndrome (GBS) is considered a clinical diagnosis; therefore, a diagnosis can be made with confidence at the bedside in most cases. History of physical, CSF analysis, electrodiagnostic studies, MRI spine MRI brain. Nerve conduction studies abnormal (normal in Miller Fisher syndrome).
Therapy Plan: intravenous immunoglobulin (IVIG) or plasma exchange.
Prognosis: Overall, most patients with GBS do well, with up to 85% of patients achieving independent ambulation with recovery around 6 months; however, there is a significant proportion of patients (20%) with morbidity. Rarely recurrent.
Differential Diagnosis: Tick paralysis.
Regular Expression: weakness
Logic Description: First occurrence of Guillain-Barre in an inpatient setting expected to last atleast 180 days.
Literature review—several literature sources cited use of codes mapping to acute infective polyneuritis as complete capture of ICD9 codes
Source of errors in real world and impact on algorithm:
- Miss rate/False negative rate - we hypothesize that it is less likely that this condition would be missed when present because of its characteristic presentation and relatively rapid onset.
- Index date misclassification: we hypothesize that because presents itself relatively rapidly and it is not an indolent disease - and so the probability of index date misclassification is lower.
- Specificity - since GB is the most common cause of acute, flaccid, neuromuscular paralysis it is unlikely to be mistaken for rare forms of acute flaccid paralysis. However, it is possible that it may mistaken for the UMN/stroke related plegia.
This cohort definition has cohort id # 235 in OHDSI Phenotype library (pending peer review).
Insights from Cohort Diagnostics:
- since this cohort definition requires inpatient or inpatient/er, data sources that do not have good capture of such visits are not good candidates (sensitivity error).
- Incidence rate: Overall annual Incidence rate: ~0.1 per 1,000 person-years, across age/sex/years is probably higher than expected. We observe that incidence increases with age decile - however we did not find that reported anywhere else. The rates also appeared to be higher in males.
- Index event breakdown: Guillain-Barré syndrome and Acute infective polyneuritis are the two most common concepts at inex. We observe Acute infective polyneuritis mostly prior to 2015 when ICD9CM vocabulary was used. In ICD10CM G61.0 concept is considered equivalent to ICD9CM 357.0. The inclusion of Fisher’s syndrome codes represents <5% patients in Optum Panther.
On Day 0: The top strengtheners in condition domain were malaise, asthenia, muscle weakness. Interestingly we also observed electrolyte imbalance. Corticosteroids utilization was high up to 80% on index date. Immunoglobulins utilization was high in JMDC and Optum EHR (80%) suggesting high specificity. Immunoglobulin utilization was not observe in other US data sources (conceptId 38003174 was present in > 30% in optum dod). There appears to be an increased utilization of gabapentin in the period immediately after diagnosis - the significance of this is unknown.
On Day -30 to -1: we observe the diagnosis of GBS in about 10% of persons. This suggest that some person were being evaluated in outpatient basis prior to inpatient stay. This is evidence of index date misclassification. Top concept in this period are GB syndrome, polyneuropathy, acute bronchitits * upper respiratory infections (common among persons with GBS syndrome, asthenia, malaise, paresethsia, hypokalemia
source of errors:
- Sensitivity errors: we require persons to have inpatient or ER visit on index. We do not know if we are missing persons who truly have guillian barre syndrome, but are not being seen in the visit classified by Inpatient or Inpatient & ER. In general we would not expect sensitivity error as this being a relatively serious condition, patients are more likely to seek care at higher acuity setting. We have not tested this assumption.
- Index date misclassification: this definition has index date misclassification because we are indexing on inpatient stay. We observe evidence that persons are being managed in non inpatient setting prior to being in an inpatient setting. So- a better cohort definition may be requiring inpatient stay at a future date.
Overall: this cohort definition appear to identify persons with the phenotype of interest. Should not be used in data sources without good capture of inpatient visit. A future work to correct index date misclassification may be needed.
Pending - PheValuator