Preventable ER Visits (OASIS Ambulatory Care Sensitive Conditions)

Limitations

OASIS's percent of emergency room visits that are for a preventable (ambulatory care sensitive) condition, among ER visits not ending in admission: not a rate per resident, and not comparable with preventable_hospitalizations' percent of stays (admitted visits are there). Conditions nest: never add them. The 2015 ICD-10-CM switch breaks several conditions (two end) and the totals by sex. Race groups start in 2016 (NULL above 20% unknown). OASIS withholds the percent on 1-4 visits (NULL). The conditions are OASIS's own list (its ACSC definitions page): conditions that timely, effective outpatient care can often keep out of the hospital, used as prevention quality indicators. It is not AHRQ's Prevention Quality Indicators (our reading: it includes dental conditions, failure to thrive and iron deficiency anemia, sets age limits only on a few conditions, and gives a percent, not a rate per resident). OASIS says the list is primarily intended for inpatient data and applies it to ER visits as well (https://oasis.state.ga.us/dtt/content/DefACSC.html). OASIS's ACSC module also returns 2000 and 2001, with no ER visit in any row (its ER data start in 2002): those years are left out, not served as zeros. The percent divides by all of the group's ER visits (every cause, injuries included), so it shows how much of a place's ER use is for these conditions: a place with many injury visits shows a lower percent for the same preventable visits. It is not comparable with preventable_hospitalizations' percent, which divides by inpatient stays (births and surgery included); the two never count the same event. A visit counts in one condition at most (OASIS reports the first one found). An ER visit is one visit to the emergency room of a non-federal hospital in Georgia by a Georgia resident, by county of residence, that did not end in an inpatient admission: OASIS counts an ER patient who is admitted as a hospital discharge and keeps the two mutually exclusive, so a preventable ER visit that ends in admission is a stay in preventable_hospitalizations, never a visit here. A person who visits twice counts twice; visits to other states' hospitals are not counted. 27% of rows with at least one preventable visit have no percent (1-4 visits, mostly small counties, groups and conditions). Where a group had no ER visits at all in a place (num_er_visits_all_causes 0) the percent is NULL: OASIS shows 0, but a percent of nothing is undefined (our mask, 90,493 rows). ICD-9-CM codes until September 2015 and ICD-10-CM from October 2015, 2015 mixing both: Georgia's kidney_or_urinary_infection 85,879 in 2014 and 8,966 in 2017; diabetes_without_complications 13,480 in 2014 and 1,880 in 2017; diabetes_with_other_complications 7,060 in 2014 and 24,706 in 2017; chronic_obstructive_pulmonary_disease 21,180 in 2014 and 49,107 in 2017; cellulitis 24,293 in 2014 and 42,830 in 2017; bacterial_pneumonia 25,142 in 2014 and 33,670 in 2017; iron_deficiency_anemia 5,364 in 2014 and 141 in 2017; vaccine_preventable_conditions 441 in 2014 and 70 in 2017. OASIS's issues page names the ER diabetes split (overall diabetes in trend). kidney_or_urinary_infection's ICD-10-CM codes (N10-N12) leave out the unspecified urinary tract infection its ICD-9-CM codes included (599.0; our reading of the fall). The groups carry their conditions' breaks: avoidable_conditions 75,658 and 67,311, acute_conditions 471,478 and 454,596, chronic_conditions 160,655 and 196,875, all conditions 707,791 and 718,782; acute_conditions and the total stay level only because breaks offset (our reading). By sex the total does not stay level: kidney_or_urinary_infection's fall is mostly women's visits (74,947 female and 10,932 male in 2014; 8,269 and 697 in 2017), so the female percent of all conditions falls from 19.17% (2014) to 17.36% (2017) while the male rises from 18.05% to 18.63%, and female, above male in 138 of 159 counties in 2014, is above it in 27 in 2016 (our reading: coding, not a change in illness). OASIS's list has 28 conditions; skin_grafts_with_cellulitis and congenital_syphilis are left out of this topic: OASIS defines the first by inpatient DRG and the second as a newborn's secondary diagnosis, so no ER visit can carry them (0 in every row of every year; our reading). Two more fall to 0 in every place and have no rows from then (dropped, not served as zeros): cervical_cancer (28 visits in 2015; no rows from 2016); pulmonary_tuberculosis (19 visits in 2016; no rows from 2017). OASIS says cervical cancer is no longer an ACSC in ICD-10; pulmonary tuberculosis has ICD-10-CM codes, but no visit carries OASIS's definition. failure_to_thrive (under age 1) falls from 41 visits in 2014 and 37 in 2015 to 6 in 2016 and 0-3 a year since; its 0s are true counts under OASIS's definition, which rarely captures failure to thrive in ICD-10-CM codes (our reading): they do not mean the condition went away. Other coding moves (our reading, kept as published): convulsions and epilepsy trade visits in 2007-2008 (convulsions 26,230 in 2006, 19,303 in 2008; epilepsy 2,071 and 10,843); cellulitis grew from 6,970 visits (2002) to 22,274 (2005); diabetes_with_ketoacidosis_or_coma fell from 1,121 (2017) to 753 (2018), undocumented; nutritional_deficiencies, which count secondary diagnoses too, grew from 39 (2002) to 1,065 (2025). Georgia's preventable ER visits fell from 747,273 in 2019 to 513,414 in 2020 (the COVID-19 pandemic). In 2025, the newest year, they fell to 648,418 (15.94% of all ER visits) from 680,529 (16.88%) in 2024, led by severe ear, nose and throat infections (216,154 to 188,511) and bacterial pneumonia (38,308, after a 2024 peak of 48,232 against 35,397 in 2023); OASIS documents no reason. The all-cause visits are er_visits_by_cause's (checked every run), so its 11 county-years whose visits drop for one year (missing hospital records, our reading) are here too; the counts drop but the percent moves much less (Walker 2007: 204 of 1,512 visits, 13.5%, against 2,708 of 15,713 in 2006 and 2,738 of 15,927 in 2008, 17.2% and 17.2%). OASIS's ER data records no ethnicity before 2016; from 2016, 9.7% to 18.2% of Georgia's preventable ER visits a year are race_unknown (unknown ethnicity), up to 99% of a county's in a year, and visits of unknown ethnicity are more often preventable (28.2% in 2024, against 16.9% for all), so the race groups' percents may run low (our reading). race_unknown, all minus the seven race groups (our calculation, both counts), is in every row OASIS's own unknown-ethnicity group, since OASIS records no non-Hispanic visit of unknown race; its percent is OASIS's. Where race or ethnicity is unknown for more than 20% of a place-year's visits (race_unknown / all, all causes), the race groups' counts and percents for that place and year are NULL (our mask, OASIS's own 20% threshold for missing items): each group's counts would miss its share of the unknowns, so its figures follow the recording, not the group. The all, sex, payer and race_unknown rows are kept, so the unknown share stays visible. It applies to 146 county-years (49 counties, never Georgia), the same as er_visits_by_cause's. Race groups follow the platform convention from OASIS's race x ethnicity cross: hispanic is Hispanic of any race; white, black, asian, native_american (American Indian or Alaska Native), pacific_islander (Native Hawaiian or Other Pacific Islander) and multiracial are non-Hispanic. A payer's percent divides by that payer's own ER visits. The payer is the primary payer as recorded on each record, and coding shifts show as jumps between payers. OASIS counts HMO and other managed care under private insurance and does not say where Medicare Advantage or Medicaid managed-care plans fall (our caution). PeachCare has no rows before 2006 (no visit recorded it, so no value can exist). OASIS's payer and race breakdowns are never crossed. Not served: OASIS's SES-vulnerability rows (their percents are valid, each dividing by the SES group's own stays or visits, but the platform has no SES group yet), age and education breakdowns. OASIS's reporting-issues page notes: no 2012 data from Hart County Hospital (Hart and nearby counties low); Candler County's hospital did not report in 2013 (Candler low; Bulloch, Evans, Emanuel and Tattnall slightly); and the ICD-10-CM switch (October 2015), after which some conditions 'appear to be out of trend' (https://oasis.state.ga.us/dtt/content/KDIACSC.html). The conditions are defined differently from er_visits_by_cause's causes: Georgia's asthma visits in 2024 are 41,017 here and 41,973 there. 2025 was added to OASIS on 2026-09-03; OASIS marks no year provisional. Counties add up to Georgia, except race groups from 2016, whose counts are NULL in the county-years the race mask covers (Georgia's race rows count every county, so a race group's counties add up to less there). tract_geoid is always NULL.