Table 3.

Overall rating and quality of evidence for measurement properties of structural validity, internal consistency, and cross-cultural/measurement invariance.^a

Study IDb	Instrument	# of factors	Structural validity		Internal consistency			Cross-cultural/ measurement invariance
			Overall rating	Quality of evidence	Overall rating	Quality of evidence	Overall rating		Quality of evidence
1-29 [24-43]	eHEALSc	1	–	Moderate	+	Moderate	+		High
30-32[31,39,44]	eHEALS	2d	–	High	+	High	N/Ae		N/A
33 [45]	eHEALS	2f	+	Low	+	Low	N/A		N/A
34 [46]	eHEALS	2g	+	Moderate	N/A	N/A	N/A		N/A
35–39 [47-50]	eHEALS	2h	–	High	+	High	N/A		N/A
40 [51]	eHEALS	2i	+	Moderate	N/A	N/A	N/A		N/A
41 [52]	eHEALS	2j	+	Moderate	+	Moderate	N/A		N/A
42 [53]	eHEALS	2k	+	Moderate	+	Moderate	N/A		N/A
43-45 [54-56]	eHEALS	3l	+	High	+	High	+		High
46 [57]	eHEALS	3m	+	Low	N/A	N/A	N/A		N/A
47 [58]	eHEALS	3n	+	High	+	High	+		High
48 [39]	eHEALS	Bifactoro	?	Low	N/A	N/A	N/A		N/A
49 [59]	eHEALS-Ep	6	+	High	+	High	N/A		N/A
50 [60]	e-HLSq	3	–	Low	N/A	N/A	N/A		N/A
51 [61]	DHLIr	7	+	Low	+	Low	N/A		N/A
52 [42]	DHLI	5	+	Low	N/A	N/A	N/A		N/A
53 [62]	eHLAs	7	?	Very low	–	Very low	N/A		N/A
54, 55 [63]	eHLQt	7	–	High	+	High	?		Low
56, 57 [64]	TeHLIu	4	+	High	+	High	N/A		N/A

^aThe item numbers of the eHEALS are those assigned in the original article by Norman and Skinner [24].

^bID: study identification number (a study identification number was assigned to each of the 57 studies in the 41 articles because some articles covered multiple studies; see Multimedia Appendix 2).

^ceHEALS: eHealth literacy scale.

^dInformation seeking (items 1, 2, 3, 4, 5, 8), information appraisal (items 6, 7) [31,39,44].

^eNo information was available in the study.

^fFactor 1 (items 1, 2, 4), factor 2 (items 3, 5, 6, 7, 8) [45].

^gFactor 1 (items 3, 4), factor 2 (items 1, 2, 5, 6, 7, 8) [46].

^hFactor 1 (items 1, 2, 3, 4, 5), factor 2 (items 6, 7, 8) [47-50].

ⁱFactor 1 (items 2, 6, 7, 8), factor 2 (items 1, 3, 4, 5) [51].

^jFactor 1 (items 1, 2, 3, 4), factor 2 (items 5, 6, 7, 8) [52].

^kInformation acquisition (items 1, 3, 4), information application (items 2, 5, 6, 7, 8) [53].

^lAwareness (items 3, 4), skills (items 1, 2, 5), evaluation (items 6, 7, 8) [54-56].

^mAwareness (items 1, 2), skills (items 4, 5), evaluation (items 6, 7, 8) [57].

ⁿInformation awareness (items 3, 4), information seeking (items 1, 5), information engagement (items 2, 6, 7, 8) [58].

^oGeneral factor (items 1, 2, 3, 4, 5, 6, 7, 8), subfactor 1 (items 1, 2, 3, 4, 5, 8), subfactor 2 (items 6, 7) [39].

^peHEALS-E: eHealth literacy scale-extended.

^qe-HLS: electronic health literacy scale.

^rDHLI: digital health literacy instrument

^seHLA: eHealth literacy assessment toolkit.

^teHLQ: eHealth literacy questionnaire.

^uTeHLI: transactional eHealth literacy instrument.