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Description

For persons eligible for the Self-Administered Questionnaire supplement, PCS reports the Physical Component Summary score for the Short-Form 12 (SF-12), measuring physical health status over a four-week recall period.

SF-12 Scoring 

The SF-12 asks questions about general health, limitations in a typical day, and limitations in the past 4 weeks. Analysis of SF-12 data relies on two summary scores: the Mental Component Summary (MCS) and the Physical Component Summary (PCS). Each summary variable includes all 12 items, but weights different items more heavily.

The PCS puts more emphasis on:

  • During a typical day, limitations in moderate activities (ADDAYA)
  • During a typical day, limitations in climbing several flights of stairs (ADCLIM)
  • During past 4 weeks, pain interfered with normal work outside the home and housework (ADPAIN)
  • During past 4 weeks, as result of physical health, accomplished less than would like (ADPALS)
  • During past 4 weeks, as result of physical health, limited in kind of work or other activities (ADPWLM)

The MCS puts more emphasis on:

  • During the past 4 weeks, felt downhearted and blue (ADDOWN)
  • During the past 4 weeks, felt calm and peaceful (ADCAPE)
  • During the past 4 weeks, as a result of mental problems, accomplished less than you would like (ADMALS)
  • During the past 4 weeks, as a result of mental problems, limited in kind of work or other activities (ADMWLM)
  • During the past 4 weeks, physical health or emotional problems interfered with social activities (ADSOCA)

If any SF-12 component item is missing, PCS cannot be computed directly, though a proprietary method for computing the scores is available from QualityMetric, Inc. Scores are calculated according to the standard algorithm and incorporate imputations for some cases with missing data; negative values are possible in rare cases. The variable SFFLAG indicates if the scores were imputed; though cases were not imputed if too much of the component information was missing.

For more information, the key reference for the SF-12 is

Ware, J.E., Kosinski, M., and Keller, S.D. (1996). A 12-item short-form health survey: Construction of scales and preliminary tests of reliability and validity. Medical Care 34:220.

Changes in Comparability for the SF-12: 2000-2002 vs. 2003 and later years 

Comparability of the raw scores between 2000-2002 and 2003 and later years is affected by a change to using SF-12 version 2 in 2003 from using SF-12 version 1 in earlier years. The PCS and MCS scores based on Version 1 of the SF-12 in these three years were based on norms from 1990, whereas SF-12 version 2 scores based on Version 2 of the SF-12 were based on norms from a 1998 national study.

To appropriately compare Version 1 with Version 2 scores, Version 1 scores need to be rescaled to 1998 norms. This can be done by adding 1.07897 to PCS scores from Version 1, and by subtracting 0.16934 from Version 1 MCS scores.

Codes

PCS is a variable with six columns and two implied decimal places. That is, values of 012345 should be interpreted as 123.45. The command files delivered with IPUMS extracts automatically divide PCS by 100, so no further adjustment is needed.

0099.96: NIU
0099.97: Unknown - refused
0099.98: Unknown - not ascertained
0099.99: Unknown - don't know

Comparability

Comparability of the raw scores between 2000-2002 and 2003 and later years is affected by a change to using SF-12 version 2 in 2003 from using SF-12 version 1 in earlier years. The PCS and MCS scores based on Version 1 of the SF-12 in these three years were based on norms from 1990, whereas SF-12 version 2 scores based on Version 2 of the SF-12 were based on norms from a 1998 national study.

To appropriately compare Version 1 with Version 2 scores, Version 1 scores need to be rescaled to 1998 norms. This can be done by adding 1.07897 to PCS scores from Version 1, and by subtracting 0.16934 from Version 1 MCS scores.

Other comparability issues:

Problem with Spanish translation in 2001

For the variable ADSOCA (Physical health or emotional problems interfering with social activities in past 4 weeks), a difference between the English and Spanish-language response categories was inadvertently introduced. The Spanish-language response categories included the category 3 ("Good bit of the time") but categories 3 and 4 from the Spanish-language version of the questionnaire were combined into category 3 ("Some of the time"). The remaining response categories from the Spanish-language version of the questionnaire were realigned to match those from the English-language version of the questionnaire.

Universe

  • 2000-2016: All adults aged 18 and older.

Availability

  • 2000-2016

Weights

Flags

SFFLAG