Provider Retention in High Need Areas. Construction of Analytic Datasets

12/22/2014

The first analytic dataset was constructed using NHSC data, P360 data and Medicare provider data. Using the name, birthdate, gender and a number of other variables, we matched the NHSC administrative file with the P360 data. This way we were able to uniquely identify about 18,500 of the 22,703 NHSC participants in the P360.6 This match gives us the participants’ NPIs as well as other important information including their location’s zip code in 2013. Almost all of these matches were associated with a valid NPI (i.e., for about 17,900 NHSC participants). The matches without an NPI correspond to NHSC participants that do not have an NPI.

The next step was to link the merged P360-NHSC file with the Medicare Provider file by NPI. The analytic file contains annual information on over 1 million non-NHSC providers as well as on 8,973 NHSC participants (out of the 17,900 participants with a valid NPI). The dataset allows us to track the annual locations at the zip code level for each year individuals are in the Medicare Provider data (i.e., over the timeframe between 2005 and 2011). Figure II.1 below summarizes the main steps we took to create the first analytic dataset.

Figure II. 1: Steps to Create the First Analytic Dataset on NHSC Providers

Steps to Create the First Analytic Dataset on NHSC Providers

As our chosen level of geography was the zip code, the next step was to determine whether the zip code associated with each provider’s location was part of a HPSA or not. For this purpose we used the dataset we received from HRSA containing information on all HPSAs and constructed an algorithm to determine whether a provider’s zip code was part of a single-county HPSA, Census tract HPSA, Census division HPSA, or a facility HPSA. Some Census tract and Census division HPSAs may straddle two or more zip codes, in which case we determined that if more than half of the zip codes’ population was within the bounds of a Census tract or Census minor civil division HPSA, those zip codes would be flagged as HPSAs. Also, we flagged the HPSA zip codes as primary care, mental health and dental HPSAs, using HRSA’s classification of HPSAs by type. An inherent limitation of this approach is that we only used data on HPSAs as of December 2013. To the extent various areas lose or gain HPSA status over our period of analysis, we may erroneously place providers in HPSAs (or non-HPSAs) in the years prior to 2013.

To ensure a consistent classification of NHSC providers and non-NHSC providers by their medical discipline, we mapped the detailed health care occupation (available in P360) of each non-NHSC participant into the corresponding NHSC discipline. The list of NHSC disciplines is presented in Table II.5 along with the distribution of providers by these disciplines in the overall population of NHSC participants and in the sample of participants we identified in the first analytic dataset. Table II.5 also provides the average age of providers (at entry in NHSC service) and the distribution by gender and HPSA type.

Table II. 5: Comparison between NHSC Providers in the Overall Population and in the First Analytic Dataset

Discipline

All NHSC Providers

NHSC in First Data Set

Allopathic Physician

4,465

2,960

Osteopathic Physician

1,382

1,010

Chiropractor

14

10

Certified Nurse Midwife

582

227

Dentist

2,508

36

Health Service Psychologist

1,768

597

Licensed Clinical Social Worker

2,208

635

Licensed Prof Counselor

1,988

66

Marriage and Family Therapist

348

14

Nurse Practitioner

3,735

1,836

Pharmacist

26

0

Physician Assistant

3,115

1,483

Psychiatric Nurse Specialist

81

44

Registered Dental Hygienist

483

19

TOTAL

22,703

8,937

Age (at Entry)

36.9

37.7

Gender

Males

6,820

3,249

Females

15,883

5,688

HPSA Type

Primary Care

12,452

6,985

Mental Health

7,260

1,897

Dental

2,991

55

TOTAL

22,703

8,973

We completed the construction of the first analytic dataset by eliminating the following groups of non-NHSC participant providers: (i) those who did not fall under any one of the NHSC discipline types; (ii) those who did not serve in HPSAs; (iii) those who served in HPSAs where no NHSC participant served over the 2005-2011 period; and (iv) specialists (cardiologists, dermatologists etc.). The purpose of these data restrictions was to ensure a degree of comparability between NHSC participants and non-NHSC participants who served in HPSAs. We ended up with a total of 202,999 non-participant providers serving in primary care HPSAs and a total of 19,304 non-participants serving in mental health HPSAs. One limitation of the analytic dataset is that it has very few dentists and pediatricians, since these providers are unlikely to file Medicare claims and thus appear in the Medicare data. The main characteristics of non-participants are presented in Table II.6.

Table II. 6: Non-NHSC Providers Serving in Primary Care and Mental Health HPSAs in the First Analytic Dataset

Characteristics

Primary Care HPSA

Mental Health HPSA

Discipline

Non-NHSC Providers

Percent

Non-NHSC Providers

Percent

Physician

168,620

83.1

9,034

46.8

Certified Nurse Midwife

572

0.3

--

--

Dentist

5,409

0.6

--

--

Health Service Psychologist

--

--

4,426

22.9

Licensed Clinical Social Worker

--

--

4,848

25.1

Licensed Professional Counselor

--

--

130

0.7

Marriage and Family Therapist

--

--

2

0.0

Nurse Practitioner

24,632

12.1

864

4.5

Physician Assistant

9,175

4.5

 

 

TOTAL

202,999

100.0

19,304

100.0

Age (at Entry)7

45.8

--

51.7

--

Gender

 

 

 

 

Males

130,046

64.1

9,427

48.8

Females

72,953

35.9

9,877

51.2

TOTAL

202,999

100.0

19,304

100.0

In Table B.3 of Appendix B we present the distribution of providers serving in NHSC in each state over the timeframe of the first analytic data.

Finally, in the case of providers who changed their location from one year to the next we constructed variables measuring the distance of the move by calculating the distance in miles between the zip code centroid of the initial location and the zip code centroid of the next year’s location.

The main advantage of the first analytic dataset stems from the fact that it allows us to track the location of providers after they complete their NHSC service. However, the number of NHSC providers is potentially limited. We therefore constructed a second analytic dataset relying only on NHSC data, P360 data and HPSA data. The main feature of this dataset is that provides information on the NHSC providers’ location in two points in time: the year of program termination and December 2013 (i.e., the time when P360 information is recorded).

The number of NHSC participants in this second dataset increases to about 18,500 (of which 17,983 have a valid NPI). As expected, the distribution of NHSC providers by discipline resembles the distribution from the overall NHSC population more closely (Table II.7). Also, the other characteristics of participants from the second dataset are more similar to the characteristics from overall population of participants. In the next chapter we compare the retention patterns of participants from the first dataset with the retention patterns of participants from the second dataset.

Table II. 7: Comparison between NHSC Providers in the Overall Population and in the Second Analytic Dataset

Discipline

All NHSC Providers

NHSC in Second Data Set

Allopathic Physician

4,465

4,151

Osteopathic Physician

1,382

1,288

Chiropractor

14

12

Certified Nurse Midwife

582

481

Dentist

2,508

1,842

Health Service Psychologist

1,768

1,272

Licensed Clinical Social Worker

2,208

1,573

Licensed Prof Counselor

1,988

1,342

Marriage and Family Therapist

348

257

Nurse Practitioner

3,735

3,058

Pharmacist

26

11

Physician Assistant

3,115

2,476

Psychiatric Nurse Specialist

81

67

Registered Dental Hygienist

483

153

TOTAL

22,703

17,983

Age (at Entry)

36.9

40.0

Gender

Males

6,820

5,775

Females

15,883

12,207

HPSA Type

Primary Care

12,452

10,729

Mental Health

7,260

5,259

Dental

2,991

1,995

TOTAL

22,703

17,983

NOTE: The total number of matched NHSC providers presented in the above table is limited to providers with a valid NPI.

Figure II.2 summarizes the main steps needed to construct the second analytic dataset.

Figure II. 2: Steps to Create the Second Analytic Dataset on NHSC Providers

Steps to Create the Second Analytic Dataset on NHSC Providers

6 The number of unique matches could have been higher, but in the case of about 1,500 participants their name was exactly the same as the name of multiple individuals in P360. As other information on these participants was unavailable in the two datasets, we were unable to uniquely identify these participants in the P360 data.

7 The average age of non-participant providers when they first appear in the Medicare data.

 

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