Appendix 1: Revised Criteria for the Unit of Analysis Error
Flowchart for the detection of the Unit of Analysis error in susceptible studies.
Addressing the Unit of Analysis- 2
Appendix 2: Susceptible Observational Studies That Addressed the Unit of
Analysis
Article
Category
Clinical
Skills
First Author, Year
of Publication, and
Reference
Type of Study
Patient Level
Sample Size
Practitioner/
Practice Level
Sample Size
Prospective Cohort
50 Patients
16 Physicians
Cross-sectional
3453 Patients
138 Physicians
Prospective Cohort
7730 Patients
300 Physicians
Retrospective
2256 Patient Visits
5 Practitioners
To assess the association between
licensing scores and quality of care
given.
Prospective Cohort
113535 Patients
614 Physicians
The effect of resident postgraduate
year on inguinal hernia recurrence.
Retrospective
Analysis
1983 Patients
Unknown
To compare the clinical performance of
primary care and medicine residents.
Prospective Cohort
6307 Patients
153 Physicians
Bach PB,
2004(60)
Baldwin LM,
1995(61)
Carey TS,
1996(62)
Chan BT,
2003(63)
To delineate differences in physicians
who care for different racial groups.
Cross-sectional
150391 Patients
4355 Physicians
To assess the effect of prior defendant
status on obstetric practice.
Retrospective
Cohort
11980 Patients
205 Physicians
To determine the variables associated
with using spinal imaging for back pain.
Prospective Cohort
1633 Patients
208 Physicians
To determine the variables associated
with referrals to specialists.
Cross-sectional
696003 Patients
6972 Physicians
Cooper LA,
2003(64)
Prospective Cohort
252 Patients
31 Physicians
Flocke SA,
2005(65)
To correlate race, patient satisfaction,
and patient-centered communication.
To determine whether physician and
patient gender influences preventative
care.
Cross-sectional
3256 Patients
138 Physicians
Franks P,
2000(66)
To examine the relationship between
referral rates, and patient satisfaction.
Cross sectional
5000 Patients
100 Physicians
Franks P,
2003(67)
To correlate socioeconomic status with
preventive care and referral patterns.
Cross-sectional
437743 Patients
568 Physicians
Gaur AH,
2005(68)
Greenfield S,
2002(69)
To determine the providers that
administer antibiotics during viral
illness.
The effects of case-mix and physicianlevel clustering on quality of care.
Cross-sectional
1952 Encounters
Unknown
Retrospective
1750 Patients
63 Physicians
Hampers LC,
2002(70)
To delineate differences in Emergency
Department management of croup.
Retrospective
Cohort
530 Patients
69 Physicians
Kalish RB,
2004(71)
To determine the rate and factors
influencing cesarean delivery.
Cross-sectional
422 Patients
422 Physicians
Mangione-Smith R,
1999(72)
The effect of parental expectation on
antibiotic prescribing rate.
Observational
306 Patients
10 Physicians
Bariciak ED,
2003(53)
Gotler RS,
2000(54)
Kaplan SH,
1996(55)
Riley MR,
2005(56)
Goal of Study
To assess ED physician accuracy in
estimating the age of bruises in
children.
To assess the means by which
physicians facilitate participatory
decision-making.
To characterize physicians who
facilitate participatory decision-making
well.
To determine how frequently pediatric
sub specialists diagnose obesity.
Educational
Tamblyn R,
1998(57)
Wilkiemeyer M,
2005(58)
Wong MD,
1999(59)
Physician
Practice
Patterns
Addressing the Unit of Analysis- 3
Mangione-Smith R,
2002(73)
To determine observational procedures
alter patterns of antibiotic prescribing.
To determine the parental beliefs
regarding antibiotics that are
attributable to race.
To determine the physician
characteristics associated with delivery
of quality care.
Observational
317 Patients
Unknown
Cross-sectional
543 Patients
38 Physicians
Cross-sectional
24581 Patients
3660 Physicians
Retrospective
104231 Patients
Unknown
Cross-sectional
303 Patients
19 Physicians
Prospective Cohort
429 Patients
132 Physicians
To identify clinician opinions associated
with continuation of exclusive
breastfeeding.
Prospective Cohort
288 Patients
121 Physicians
The effects of physician behavior on
child immunization rates.
Retrospective and
cross-sectional
1834 Patients
15 Physicians
To compare cardiologists and
generalists regarding resource use and
outcomes.
Prospective Cohort
1298 Patients
Unknown
The effect of hospitalist care on
resource use and outcome.
Retrospective
Cohort
5308 Patients
138 Physicians
To determine the inter-rater reliability of
the EQ-5D in patients with dementia.
Cross-sectional
64 Patients
4 Physicians
To determine the effect of patient age
on end-of-life care.
The association between malpractice
records and patient complaints.
Prospective Cohort
Retrospective
Cohort
9105 Patients
Unknown
Unknown
645 Physicians
Retrospective
1308 IVF Egg
Transfers
11 Physicians
Retrospective
Cohort
652 Patients
399 Physicians
The causes of variability in IVF success
rate between individual practitioners.
Retrospective
782.1 IVF Transfer
Cycles
13 Physicians
Meltzer D,
2002(89)
To compare costs and outcomes
between hospitalists and generalists.
Prospective Cohort
6511 Patients
60 Physicians
Meredith LS,
2005(90)
The effect of provider’s attitudes on
smoking cessation.
Retrospective
1080 Patients
280 Physicians
The relationship between physician
certification and clinical performance.
Cross-sectional
197500 Patients
1982 Physicians
The effect of interprovider variability on
cost variations in ventilated neonates.
Retrospective
Cohort
132 Patients
11 Physicians
The effect of a change to fixed distance
embryo transfer on IVF success.
Retrospective
4439 IVF Transfer
Cycles
7 Physicians
The effect of interprovider variability on
pregnancy rates in in vitro fertilization.
Prospective
Observational
997 Egg Transfers
6 Physicians
Comparison of the quality of HIV care
between Physicians, PA’s and NP’s.
Cross-sectional
6651 Patients
243 practitioners
Mangione-Smith R,
2004(74)
Pham HH,
2005(75)
Rathore SS,
2001(76)
Silliman RA,
1999(77)
Taveras EM,
2004(78)
Taveras EM,
2004(79)
Taylor JA,
1997(80)
The effect of physician gender on rate
of post-MI cardiac catheterization.
The effect of surgeon gender on
treatment offered for early-stage breast
cancer.
To assess attitudes and gaps in
clinician counseling for breastfeeding
mothers.
QI and
Outcome
Auerbach AD,
2000(81)
Auerbach AD,
2002(82)
Coucill W,
2001(83)
Hamel MB,
1999(84)
Hickson GB,
2002(85)
Karande VC,
1999(86)
Keating NL,
2004(87)
Lalwani S,
2004(88)
Miller G, 2004(91)
Perlstein PH,
1997(92)
Van De Pas MM,
2003(93)
Van Weering HG,
2005(94)
Wilson IB,
2005(95)
The effect of interprovider variability on
the success of IVF-ET.
The effect of different practice
management strategies on diabetes
quality of care.
Addressing the Unit of Analysis- 4
Appendix 3: Susceptible Observational Studies That Did Not Address the
Unit of Analysis
Article
Category
First Author, Year
of Publication, and
Reference
Practitioner/
Practice Level
Sample Size
Goal of Study
Type of Study
Patient Level
Sample Size
Lehmann CU,
2004(96)
Pestotnik SL,
1996(97)
Potts AL,
2004(98)
The effects of an online TPN
calculator on physician error rate.
Prospective Cohort
1684 Patient
Orders
Unknown
The effects of a CDSS on appropriate
clinical and financial use of antibiotics.
Prospective
Observational
162196 Patients
Unknown
The effects of CPOE on medical
errors.
Prospective Cohort
564 Patients
Unknown
McLennan MT,
2005(99)
The association between bladder
perforation and physician experience.
Prospective
Observational
278 Patients
23 Physicians
Posther KE,
2005(100)
The number of lymph node
dissections needed to identify
malignancy.
Prospective
Observational
5237 Patients
198 Physicians
Bailit JL,
2004(101)
The effects of housestaff work hours
on errors and outcomes.
Case-control
Unknown
Unknown
Petersen LA,
1994(102)
The effect of lowered continuity of
care on adverse housestaff events.
Case-control
162 Patients
39 Physicians
Chen J, 2001(18)
The difference in cardiac
catheterization rate attributable race.
Retrospective
39715 Patients
17138 Physicians
To determine whether medical
student presence effects clinician
time.
Cross-sectional
452 Patients
16 Physicians
To assess levels of compliance with
the acute otitis media guidelines.
Cross-sectional
567 Patients
29 Physicians
The effects of physician decisionmaking styles on admission rates for
MI.
Retrospective
787 Patients
Unknown
50 Physicians
(study 1) 127
Physicians (study
2)
CDSS
Clinical
Skills
Educational
Physician
Practice
Patterns
Frank SH,
1997(103)
Garbutt J,
2003(104)
Green LA,
1994(105)
Hall JA,
1994(106)
Hampers LC,
1999(107)
Hueston WJ,
1994(19)
The relationship between physician
and gender, and patient satisfaction.
Observational
100 Patients (study
1) 537 Patients
(study 2)
To determine how language barriers
effect ED management.
Prospective Cohort
2467 Patients
Unknown
OB provider characteristics
associated with epidural use.
Retrospective
8229 Patients
392 Physicians
Kaplan SH,
1995(108)
Patient characteristics supporting
participatory decision-making.
Observational
8316 Patients
344 Physicians
Letourneau MA,
2003(109)
The characteristics of calls to
telephone neurology nursing line.
Cross-sectional
208 Patients
4 Physicians
O'Brien SH,
2004(110)
Psaty BM,
1995(111)
The performance of in managing
pediatric obesity.
The effect of clinical trials on
antihypertensive prescribing patterns.
Observational
244 Patients
Unknown
Prospective Cohort
5201 Patients
Unknown
Addressing the Unit of Analysis- 5
Ransom SB,
1996(112)
Rose JH,
2000(113)
Todd KH,
1994(114)
The effect of different reimbursement
models on surgery rates.
Retrospective
3780 Visits
Unknown
To compare cancer care offered by
oncologists with generalists.
Prospective Cohort
642 Patients
97 Physicians
The effect of patient ethnicity on
extremity trauma pain.
Prospective Cohort
207 Patients
65 Physicians
Carroll AE,
2003(115)
Chen SC,
2003(116)
Diamond HS,
1998(117)
Gillison EW,
2002(11)
Greenfield S,
1995(118)
Gregory D,
2003(119)
To quantify the predictors of resident
documentation discrepancy.
To compare the diagnostic accuracy
of two different biopsy techniques
Retrospective
339 Patient Notes
Unknown
Retrospective
232 Patients
Unknown
Retrospective
Cohort
11464 Patients
131 Physicians
Retrospective
1125 Patients
64 Physicians
Observational
1720 Patients
367 Physicians
Case-control
402 Patients
Unknown
Cross-sectional
Retrospective
Cohort
10608 Patients
360 Physicians
36103 Patients
Unknown
Prospective Cohort
652 Patients
46 Physicians
Prospective Cohort
13057 Patients
360 Physicians
QI and
Outcome
Grumbach K,
1999(120)
King WJ,
2003(121)
Martling A,
2002(122)
Selby JV,
1999(123)
The effect of full-time hospitalists on
cost of care and outcome.
The effects of care in a large center
on esophageal cancer outcome.
The effects of differing systems of
care on diabetes and hypertension.
The impact of a hospitalist program
on cost and length of stay.
The association between HMO
physician specialty and patient
satisfaction.
The effect of computerized physician
order entry on medication errors.
The effects of interprovider variability
on total excision of rectal cancer.
The effect of HMO physician specialty
on utilization and cost.