Clinimetric properties of the electronic Pain Assessment Tool (ePAT) for aged-care residents with moderate to severe dementia

Figures & data

Table 1 No pain vs pain using the electronic Pain Assessment Tool

Pain score	Category	Rest	Move	Total
0–6	No pain	73	24	97
≥7	Pain	131	172	303
Total		204	196	400

Table 2 No pain vs pain using the Abbey Pain Scale

Pain score	Category	Rest	Move	Total
0–2	No pain	69	24	93
≥3	Pain	135	172	307
Total		204	196	400

Table 3 Contingency (2×2) table for accuracy statistics

Pain score results			APS score		Total
			Pain
			Present (APS ≥3)	Absent (APS ≤2)
			307	93	400
ePAT score	Pain	Positive (present, ePAT ≥7)	295 (TP)	8 (FP)	303
		Negative (absent, ePAT 0-6)	12 (FN)	85 (TN)	97

Abbreviations: ePAT, electronic Pain Assessment Tool; APS, Abbey Pain Scale; TP, true positive; FP, false positive; FN, false negative; TN, true negative.

Table 4 Calculations of sensitivity, specificity, accuracy, likelihood ratios, and predictive values before prevalence adjustment

Clinimetric parameter	Formula	Value	95% CI
Sensitivity	(TP/[TP + FN]) ×100	96.1%	93.9%–98.3%
Specificity	(TN/[TN + FP]) ×100	91.4%	85.7%–97.1%
Positive likelihood ratio	Sensitivity/100 – specificity	11.2	5.8–21.7
Negative likelihood ratio	100 – specificity/sensitivity	0.04	0.02–0.07
Positive predictive value	(TP/[TP + FP]) ×100	97.4%	95.6%–99.2%
Negative predictive value	(TN/[TN +FN)) ×100	87.6%	81.1%–94.2%
Pain prevalence	([TP + FN]/[TP + TN + FP + FN]) ×100	76.8%	72.3%–80.8%
Accuracy	([TP + TN]/[TP + TN + FP + FN]) ×100	95.0%	92.9%–97.1%

Note: All values approximated to closest decimal point.

Abbreviations: TP, true positive; FP, false positive; FN, false negative; TN, true negative.

Figure 1 Electronic Pain Assessment Tool (ePAT) receiver-operating characteristic curve.

Note: Data shown in the graph were based on pain prevalence of 50% (ie, after adjustment).

Table 5 ROC curve characteristics, optimal criterion, and calculated sensitivity and specificity after prevalence adjustment

Parameters used in ROC curve analysis
Variable under investigation	ePAT
Classification variable (pain)	APS
Number of pain assessments (paired)	400
Positive group	307 (76.8%)
Negative group	93 (23.2%)
Pain prevalence (%)	50
Area under the ROC curve (AUC)
Area under the ROC curve (AUC)	0.98
Standard Error	0.00572
95% Confidence interval	0.96–0.99
z statistic	83.9
Significance level P (Area=0.5)	<0.0001
Youden index
Youden index J	0.88
95% Confidence intervala	0.82–0.92
Associated criterion	>7
95% Confidence intervala	>6 to >8
Sensitivity	91.2
Specificity	96.8
Optimal criterion
Optimal criteriona	>6
95% Confidence intervalb	>6 to >7
Sensitivity	96.1
Specificity	91.4

Notes:

a Taking into account disease prevalence (50%) and estimated costs: cost False Positive: 1; cost False Negative: 1 cost True Positive: 0; cost True Negative: 0 Positive group= pain present, Negative group= pain absent;

b BC_a bootstrap confidence interval (1000 iterations; random number seed: 978).

Abbreviations: ePAT, electronic Pain Assessment Tool; ROC, receiver-operating characteristic; BC_a, bias corrected and accelerated.