The 1989 NHIS Field Representative's Manual described "specialty health care plans" "that pay only for a specific health care service, such as prescriptions, cancer treatment, or eye care" as "a relatively new concept in health care insurance." The Manual further stated that such a plan "is usually limited to one type of service and is frequently obtained to supplement a comprehensive plan that may not provide that type of coverage." For 1993 forward, single service plans are defined as plans that pay for only type of service.

For all years, persons who reported having insurance that paid for only one type of care were asked what type of service was covered. For 1999, interviewers first asked an opening question about whether the person had some form of health insurance, and then asked only those with an affirmative response about single service coverage (including dental care). For 2000 forward, even persons who chose the category "no coverage of any type" in response to the opening question received the question for SDENTAL.

For further information about how the NHIS collected information about dental coverage, either as part of comprehensive plans or as single service plans, see the variable description for DENTALCOVR.

1999 forward

• What type of service or care do {your/subject name's} single service plan or plans pay for? (Mark all that apply)

• What type of service or care does the plan pay for? Mark (X) only one type of service

• What type of service does --'s plan pay for?

Starting in 1997, NCHS staff evaluated mismatches between verbatim insurance plan names and the type of coverage reported by respondents, and reclassified misreported cases into the proper category. (For a description of the back-editing process, see HIPRIVATEE.) Prior to 1997, individuals may have mistakenly reported having a single service plan, but their responses were not edited for accuracy; after 1997, responses were checked and corrected. This difference reduces the comparability of SDENTAL over time, and users should be cautious about comparing results from before and after 1997.

The back-edited and recoded variable SINGLEE, available for 1997 forward, indicates whether an individual had any single service plan. The NCHS strongly advises analysts to use these recoded insurance variables as a more reliable source of information about the types of insurance coverage than is provided by respondents' original and unedited answers about their insurance type.