Table 2.
Details of included studies
| Source/condition | Design | Population/denominator | Timescale | Case ascertainment method | Diagnostic method | Outcome | Potential bias/methodological limitations |
|---|---|---|---|---|---|---|---|
| Abhinav etal. (2007) [1] ALS | Population-based study of incidence and prevalence | South East London boroughs (Lambeth, South-wark, Lewisham, Bexley, Greenwich, Bromley), Brighton and Hove, East Sussex, and Kent; population of 2,890,482 based on 2001 census (excluding population under 15 years of age) | Incidence between January 1, 2002, and June 30, 2006; prevalence on June 30,2006 | SEALS registry used to identify cases since 1997; department general hospitals, neurology units checked; list of patients referred to healthcare professionals with suspected ALS assessed to ensure maximum ascertainment | El Escorial criteria cases (suspected, possible, probable and definite); diagnosed by 2 consultant neurologists, and review of case notes to confirm diagnoses | 138 incident cases during time period; 142 alive on point prevalence date; incidence of 1.06/100,000 person-years; prevalence of 4.91/100,000 | Possibility of low levels of missed case ascertainment in elderly category where patients seen by geriatricians not covered by capture sources; however, ascertainment likely to be high due to multiple overlapping sources |
| Forbes etal. (2007) [2] ALS | Population-based study of incidence | Scotland; population estimated at 5,125,000 in mid-1994 | Incidence from January 1,1989, to December 31, 1999 | Cases identified from national register of MND since 1989; neuroreferrals, nurse specialist records, Scottish morbidity records and mortality coding checked to ensure maximum case ascertainment | WFN criteria before 1994; El Escorial criteria after 1994; not specified which El Escorial categories included | 1,226 incident cases; incidence of 2.4/100,000 person-years | Estimated that 2.2% of patients went unobserved from the 2-source capture-recapture method; therefore, reported statistics possibly underestimated; inclusion of this estimate would increase incidence to 2.44/100,000 person-years |
| Johnston etal. (2006) [3] ALS | Population-based study of incidence and prevalence | London boroughs of Lambeth, Southwark and Lewisham; population of approx. 615,040 based on Office for National Statistics | Incidence from January 1,1997, to July 31, 2004; prevalence on July 31, 2004 | Cases ascertained from the ALS ward and clinic, neurophysiology department and physiotherapy department at King's College Hospital; records from National Hospital, Queen Square, also assessed | El Escorial criteria (suspected, possible, probable and definite cases); also assessed El Escorial definite and probable cases only, and the revised WFN criteria | El Escorial criteria:
|
Below-average proportion of elderly individuals in the population (5 vs. 7.6% national average) likely to result in lower incidence in population; however, this is a population trait rather than a methodological limitation |
| Mitchell etal. (1998) [4] ALS | Population-based study of incidence | Lancashire and South Cumbria; population of 1,473,153 based on 1991 census | Incidence from January 1,1989, to December 31, 1993 | Cases ascertained from clinical records at the Preston Department of Neurology and Neuro-physiology, and district general hospitals – these units cover the entire study catchment area; small numbers of patients living in study catchment ascertained from departments serving neighbouring catchments | Detailed clinical assessment, full inpatient investigation including: EMG, nerve conduction, muscle biopsy, CT, myelography, CSF, immunoelectrophoresis, glucose tolerance and thyroid function; assessments made by at least 2 consultant neurologists before definitive diagnosis | Incidence of 1.76/100,000 person-years | Study did not use standardised diagnostic criteria as before El Escorial; however, extensive methods used in diagnosis; case ascertainment likely to be close to fully complete as study centres are English steering centres for European MND registry, which requires a 'true' population-based knowledge of all MND patients living in the catchment |
| James etal. (1994) [5] ALS | Population-based study of prevalence | South and Mid Glamorgan, and Gwent; population of 1,394,400 based on 1991 census | Prevalence estimated on June 22,1992 | Inpatient register at the department of neurology and GP registers within the catchment area | WFN criteria (suspected, possible, probable and definite cases); WFN criteria definite and probable cases only also assessed | Prevalence of 4.02/100,000 for all cases; prevalence of 2.73/100,000 for definite and probable cases at diagnosis | None identified |
ALS = Amyotrophic lateral sclerosis; SEALS = South-East England Register for Amyotrophic Lateral Sclerosis; MND = motor neurone disease; GP = general practitioner; EMG = electromyography; CSF = cerebrospinal fluid.