Measuring prevalence and incidence of chronic conditions in claims and electronic health record databases

Figures & data

Figure 1 Definitions of observable person-time, in claims data (A) or EHR data (B).

Notes: As shown by a hypothetical patient in (A), claims data observability can be based on the entire time enrolled in a health plan (OC1) or enrolled time that excludes time known to be structurally nonobservable, eg, time during nursing home care (OC2). As shown for a different hypothetical patient in (B), EHR observability can be based on all calendar time, irrespective of event data, assuming that all patient encounters would be captured in that EHR system (OE1), time between the start of the first event and the end of the last event recorded in the EHR system (OE2), or time defined by a “buffer” around each encounter, excluding the time where there is a gap of a certain duration (eg, >365 days) between margins (OE3).
Abbreviations: EHR, electronic health record; OC, observable person-time in claims databases; OE, observable person-time in EHR databases.

Figure 2 The period of interest and the lookback time.

Notes: Timeline showing 2012 through the end of 2014, with 2014 being the POI and two different LB times, LB1 (all time) and LB2 (1 year fixed time). The observable times of three different hypothetical patients are shown.
Abbreviations: LB time, lookback; POI, period of interest.

Figure 3 The prevalence numerator.

Notes: PN1 is the point PN, ie, the condition is present as of the first day of the period of interest; and PN2 is the period PN, ie, the condition is either present as of the first day of the POI, or is recorded for the first time during the POI. These are shown for three hypothetical patients. In (A), all time LB (LB1) is used to define the LB time. In (B), fixed-time LB (LB2) is used to define the LB time. The columns at the right indicate the numbers each patient contributes to the respective numerator value, as well as the total numerator values.
Abbreviations: LB, lookback time; PN, prevalence numerator; POI, period of interest.

Figure 4 The prevalence denominator results.

Notes: Day 1 population (PD1), complete-period population (PD2), and sufficient-time population (PD4) are shown for three hypothetical patients. For PD4, assume that the requirement is defined as having at least n=90 observable person-days in the period of interest (POI). The columns at the right indicate the numbers each patient contributes to the respective denominator value, as well as the total denominator values.
Abbreviations: LB, lookback time; LO, lookback observability; PD, prevalence denominator; POI, period of interest.

Table 1 Combinations of prevalence numerator and denominator definitions

Numerator	Denominator	Notes
PN1	PD1	Reasonable estimate of the denominator combined with a numerator that appropriately does not consider the condition over the POI.
PN1, PN2	PD2	Most conservative estimate of the denominator; numerators are both appropriate.
PN1	PD3	Maximizes the denominator; PN1 gives a fair estimate of the numerator as patients may not be in the cohort for the entire POI.

Abbreviations: PD, prevalence denominator; PN, prevalence numerator.

Figure 5 The incidence numerator and denominator.

Notes: Five hypothetical patients are shown. The columns at right indicate the numbers each patient contributes to the respective numerator or denominator value, as well as the total values, assuming options IPD1 or IRD are used. Dashes (“–”) indicate that the patient was excluded from contributing to the respective value.
Abbreviations: IN, incidence numerator; IPD, incidence proportion denominator; IRD, incidence rate denominator.

Table 2 Summary of the discussed design choices for prevalence and incidence studies

Design component	Option	Short description	Long description
Observability	OC1	Enrollment	(Claims databases) Enrollment is used as a proxy for observability.
	OC2	Enrollment, excluding structurally nonobservable time	(Claims databases) Enrollment is used as a proxy for observability, but time that is known to be structurally nonobservable is excluded.
	OE1	All time	(EHR databases) Patients are assumed to be observable at all times.
	OE2	First to last event	(EHR databases) Patients are assumed to be observable from the start of their first observed event to the end of their last observed event.
	OE3	Event time margins and excluded gaps	(EHR databases) Each event is assigned a margin of time, and substantial gaps of time between these margins are excluded from observable time. In addition, time that occurs before the start of the first margin and after the end of the last margin is excluded.
POI	(N/A)	(N/A)	The window of calendar time in which prevalence or incidence is to be measured.
Lookback time	LB1	All time	The lookback time starts at the beginning of all data in the database and ends on the day before the start of the POI.
	LB2	Fixed time	The lookback time starts a fixed amount of time prior to the start of the POI and ends on the day before the start of the POI.
Lookback observability requirement	LO1	No requirement	Patients are not excluded based on observability of the lookback time.
	LO2	All lookback time	Patients are excluded if the lookback time is not completely observable.
Prevalence numerator	PN1	Point prevalence numerator	The number of patients observed to have the condition – on the first day of the POI or in the lookback time.
	PN2	Period prevalence numerator	The number of patients observed to have the condition – in the POI or in the lookback time.
Prevalence denominator	PD1	Day 1 population	The number of patients who contributed an observable person-day on the first day of the POI.
	PD2	Complete-period population	The number of patients who contributed all possible observable person-days within the POI.
	PD3	Any-time population	The number of patients who contributed ≥1 observable person-days within the POI.
	PD4	Sufficient-time population	The number of patients who contributed at least “n” observable person-days within the POI; n≥1
Incidence numerator	IN	(N/A)	The number of patients who did have the disease observed in the POI, were at risk for onset of disease, and did not have disease observed in the lookback time.
Cumulative incidence denominator	IPD1	At-risk, Day 1 population	The number of patients who were at risk for onset of disease and who contributed an observable person-day on the first day of the POI.
	IPD2	At-risk, complete-period population	The number of patients who were at risk for onset of disease and who contributed all possible observable person-days within the POI.
	IPD3	At-risk, any-time population	The number of patients who were at risk for onset of disease and who contributed all ≥1 person-days within the POI.
	IPD4	At-risk sufficient-time population	The number of patients who were at risk for onset of disease and who contributed at least “n” observable person-days within the POI; n≥1.
Incidence rate denominator	IRD	Person-time at risk	The amount of observable person-time in the POI at risk for onset of disease.

Abbreviations: EHR, electronic health records; IN, incidence numerator; IPD, incidence proportion denominator; IRD, incidence rate denominator; LB, lookback time; LO, lookback observability; N/A, not applicable; OC, observable person-time in claims database; OE, observable person-time in EHR databases; PD, prevalence denominator; PN, prevalence numerator; POI, period of interest.

Table 3 Published prevalence and incidence estimates for the selected diseases

Country	Estimate	COPD	Psoriasis	Inflammatory bowel diseasea	Schizophrenia	Cystic fibrosis
UK USA/Canadac	Annual incidence	0.2%^Citation24	0.3%^Citation25	0.01%^Citation26,Citation27	0.03%^Citation28	0.0005%^Citation29b
	Prevalence	1.9%^Citation30	1.9%^Citation31	0.2%^Citation26,Citation27	0.3%^Citation28	0.02%^Citation29b
	Annual incidence	0.9%^Citation32d	0.1%^Citation33	0.01%^Citation34,Citation35	0.04%^Citation36d	0.0003%^Citation37b
	Prevalence	4.9%^Citation38	3.2%^Citation39	0.2%^Citation40	0.3%^Citation41	0.01%^Citation37b

Notes: Annual cumulative incidence and prevalence were obtained from the indicated studies. Cumulative incidence was estimated from incidence rates when cumulative incidence was not directly reported.

a Estimates pertain to ulcerative colitis.

b Approximated based on the reported patient number (assuming complete population coverage by the respective registries) and the UK⁴² or US⁴³ total populations in 2014 or 2011, respectively.

c COPD incidence in the USA was not available; instead, results from a Canadian study are reported for this estimate.

d Estimated in patients aged 15–29 years.

Table 4 Case definitions

Case	1	2	3	4
POIs	2011, 2012, 2013, and 2014
Observable time	CPRDa; MarketScan: enrollment (OC1)
Lookback observability exclusion	None (LO1)
Prevalence numerator	Point prevalence (PN1)
Lookback time	1 year (LB2)	2 years (LB2)	All time (LB1)	All time (LB1)
Prevalence denominator	Day 1 (PD1)	Day 1 (PD1)	Day 1 (PD1)	Complete period (PD2)
Incidence denominator	Day 1 (IPD1)	Day 1 (IPD1)	Day 1 (IPD1)	At risk, complete period (IPD2)

Notes:

a In CPRD, patients were defined as observable between the latest of the up-to-standard date or the current registration date and the earliest of the last collection date, transferred out date, or date of death, during times when they were also considered “Acceptable”. No exclusions based on structurally nonobservable time were performed.

Abbreviations: CPRD, Clinical Practice Research Datalink; IPD, incidence proportion denominator; LB, lookback time; LO, lookback observability; OC, observable person-time in claims database; PD, prevalence denominator; PN, prevalence numerator; POI, period of interest.

Figure 6 Incidence and parameter estimates, by case examples, in CPRD.

Notes: Cumulative incidence (“incidence”) and point prevalence (“prevalence”) estimates are shown for each of the four cases, across multiple diseases. Case 1: 1-year lookback; Day 1 population. Case 2: 2-year lookback; Day 1 population. Case 3: all-time lookback; Day 1 population. Case 4: all-time lookback; complete-time population. Shaded regions indicate 95% confidence intervals. Tabular estimates are provided in Table S4.
Abbreviation: CRPD, Clinical Practice Research Datalink.

Figure 7 Incidence and parameter estimates, by case examples, in MarketScan.

Notes: Cumulative incidence (“incidence”) and point prevalence (“prevalence”) estimates are shown for each of the four cases, across multiple diseases. Case 1: 1-year lookback; Day 1 population. Case 2: 2-year lookback; Day 1 population. Case 3: all-time lookback; Day 1 population. Case 4: all-time lookback; complete-time population. Shaded regions indicate 95% confidence intervals. Tabular estimates are provided in Table S5.

Chronic Obstructive Pulmonary Disease (COPD) Statistics [homepage on the Internet]British Lung Association Available from: https://statistics.blf.org.uk/copdAccessed October 30, 2018

 Google Scholar

KhalidJMGlobeGFoxKMChauDMaguireAChiouCFTreatment and referral patterns for psoriasis in United Kingdom primary care: a retrospective cohort studyBMC Dermatol2013131923957883

 PubMedGoogle Scholar

BurischJJessTMartinatoMLakatosPLECCO-EpiComThe burden of inflammatory bowel disease in EuropeJ Crohns Colitis20137432233723395397

 PubMed Web of Science ®Google Scholar

RubinGPHunginAPKellyPJLingJInflammatory bowel disease: epidemiology and management in an English general practice populationAliment Pharmacol Ther200014121553155911121902

 PubMed Web of Science ®Google Scholar

KirkbrideJBErrazurizACroudaceTJIncidence of Schizophrenia and Other Psychoses in England, 1950–2009: a Systematic Review and Meta-AnalysesPLoS One201273e3166022457710

 PubMed Web of Science ®Google Scholar

Annual Data Report 2016UK Cystic Fibrosis Registry2017160 Available from: https://www.cysticfibrosis.org.uk/~/media/documents/the-work-we-do/uk-cf-registry/2016-registry-annual-data-report.ashx?la=enAccessed July 25, 2018

 Google Scholar

RamsayGQuality and Outcomes Framework – Prevalence, Achievements and Exceptions Report2016143 Available from: https://files.digital.nhs.uk/publicationimport/pub22xxx/pub22266/qof-1516-rep-v2.pdfAccessed June 01, 2018

 Google Scholar

SeminaraNMAbuabaraKShinDBValidity of The Health Improvement Network (THIN) for the study of psoriasisBr J Dermatol2011164360260921073449

 PubMed Web of Science ®Google Scholar

GershonASWangCWiltonASRautRToTTrends in chronic obstructive pulmonary disease prevalence, incidence, and mortality in Ontario, Canada, 1996 to 2007: a population-based studyArch Intern Med2010170656056520308643

 PubMed Web of Science ®Google Scholar

IcenMCrowsonCSMcEvoyMTDannFJGabrielSEMaradit KremersHTrends in incidence of adult-onset psoriasis over three decades: a population-based studyJ Am Acad Dermatol200960339440119231638

 PubMed Web of Science ®Google Scholar

The Facts About Inflammatory Bowel DiseasesCrohn’s & Colitis Foundation of America2014124 Available from: http://www.crohn-scolitisfoundation.org/assets/pdfs/updatedibdfactbook.pdfAccessed July 25, 2018

 Google Scholar

ShivashankarRTremaineWJHarmsenWSLoftusEVJrIncidence and Prevalence of Crohn’s Disease and Ulcerative Colitis in Olmsted County, Minnesota From 1970 Through 2010Clin Gastroenterol Hepatol201715685786327856364

 PubMed Web of Science ®Google Scholar

BresnahanMABrownASSchaeferCABeggMDWyattRJSusserESIncidence and cumulative risk of treated schizophrenia in the prenatal determinants of schizophrenia studySchizophr Bull200026229730810885632

 PubMed Web of Science ®Google Scholar

Cystic Fibrosis FoundationAnnual Data Report2016 Available from: https://www.cff.org/Research/Researcher-Resources/Patient-Registry/2016-Patient-Registry-Annual-Data-Report.pdfAccessed July 25, 2018

 Google Scholar

American Lung AssociationEstimated Prevalence and Incidence of Lung Disease2014165 Available from: http://www.lung.org/assets/documents/research/estimated-prevalence.pdfAccessed June 01, 2018

 Google Scholar

RachakondaTDSchuppCWArmstrongAWPsoriasis prevalence among adults in the United StatesJ Am Acad Dermatol201470351251624388724

 PubMed Web of Science ®Google Scholar

KappelmanMDRifas-ShimanSLKleinmanKThe prevalence and geographic distribution of Crohn’s disease and ulcerative colitis in the United StatesClin Gastroenterol Hepatol20075121424142917904915

 PubMed Web of Science ®Google Scholar

DesaiPRLawsonKABarnerJCRascatiKLEstimating the direct and indirect costs for community-dwelling patients with schizophreniaJ Pharm Health Serv Res201344187194

 Google Scholar

UK Population Estimates [homepage on the Internet]Office of National Statistics; 1851 to 2014 Available from: https://www.ons.gov.uk/peoplepopulationandcommunity/populationandmigration/populationes-timates/adhocs/004356ukpopulationestimates1851to2014Accessed October 30, 2018

 Google Scholar

National Population Totals [homepage on the Internet]: US Census Bureau2010–2016 Available from: https://www.census.gov/data/tables/2016/demo/popest/nation-total.htmlAccessed October 30, 2018

 Google Scholar