Table 2.

Multivariable Zero-Inflated Poisson Regression Model Summaries

Model and Variable	Parameter Estimate	Standard Error	p-value	Change in Outcome per 1 SD Increase in Predictor (%)*
Model 1: All units†,‡
(A) Dependent variable = Number of HAPU-any stage N = 656 units
Poisson equation covariates
LOS time of study	0.049696	0.005062	<.0001	23.2
Licensed HPPD	−0.089453	0.021995	<.0001	−13.1
% Risk assess within 24 hours of admission	−0.020248	0.007991	.0113	−6.2
Logistic equation covariates¶				% units without HAPU-any stage = 25.0%
% Patients “at risk” at study	−0.026990	0.012461	.0303	↑17.7% pts. “at risk” →17.1% without HAPU-any stage (OR = 0.62)
% Male patients	−0.045280	0.019379	.0195	↑12.3% Male pts. →16.0% without HAPU-any stage (OR = 0.57)
(B) Dependent variable = Number of HAPU-II+N=513 units
Poisson equation covariates
% Patients “at risk” at study	0.009867	0.002831	.0005	19.0
Licensed HPPD	−0.090562	0.031979	.0046	−13.2
Pt. (bed) turnover	−0.010134	0.002662	.0001	−20.4
Logistic equation covariates§				% units without HAPU-II+ = 38.0%
LOS time of study	−0.194533	0.082874	.0189	↑4.2 in days LOS=21.2% without HAPU II+ (OR = 0.44)
Model 2: RN education subsample†,¶,**
(A) Dependent variable = Number of HAPU-any stage—N = 135 units
Poisson equation covariates
LOS time of study	0.049148	0.007451	<.0001	22.9
Total HPPD	−0.107995	0.050902	.0339	−18.6
Patient (bed) turnover	−0.013028	0.003774	.0006	−25.4
RN experience	−0.058446	0.021388	.0063	−15.6
% Contract hours	0.027882	0.013855	.0442	15.7
(B) Dependent variable = Number of HAPU-II+—N = 135 units
Poisson equation covariates
LOS time of study	0.047619	0.008825	<.0001	22.1
Patient (bed) turnover	−0.018689	0.005034	.0002	−34.3
RN experience	−0.062537	0.027533	.0231	−16.6

Note: All Ns are the number of units with valid data for variables included in the model.

^*Measures % change in mean outcome count for changes in significant covariates.

^†A “standard set” of control variables added to all models and not specified in the table included average patient age, percent of medical patients, average number of patients in HAPU prevalence studies (a measure of unit size), hospital ownership type (government, corporate system, for-profit, and other not-for-profit), and teaching status.

^‡Additional unit and hospital characteristic not included in models 1A and B, but tested as covariates and found not significant included: total hours of nursing care per patient day; number of RN, LVN, unlicensed, or contracted care hours as percent of total care hours; RN voluntary turnover; hospital urban/rural setting; skin assessment documented within 24 hours of admission and specific prevention protocols or interventions implemented at the time of the study for patients with HAPU risk.

^§Measures change in the probability of belonging to units without HAPU-Any Stage or HAPU-II+ for changes in significant covariates.

^¶There were no significant covariates in the logistic equation for this model.

^**Additional unit and hospital characteristic not included in models 2A and B, but tested as covariates and found not significant included: percent male or female patients; licensed hours of nursing care per patient day; number of RN, LVN, or unlicensed care hours as percent of total care hours; RN voluntary turnover; hospital urban/rural setting; percent of patients at-risk for pressure ulcers; pressure ulcer risk assessment documented within 24 hours of admission; skin assessment documented with 24 hours of admission and specific prevention protocols or interventions implemented at the time of the study for patients with HAPU risk. Nonsignificant RN expertise covariates included percent with certification in a functional or clinical area; percent with a baccalaureate or higher degree in nursing, and age.