Searching from Medline and Scopus databases identified 1,104 and 1,224 articles, respectively. After deleting duplications, 1460/1,693 studies were screened by screening titles and abstracts. A total of 233 full articles were reviewed and 58 studies met inclusion criteria and were finally included in the review. Among the included studies, 50(10, 12, 20-67), 4(68-71) , and 4(7, 72-74) studies assessed CBPM, HBPM, and both CBPM and HBPM performances, respectively (see Figure 1). Their characteristics are described in Table 1. Among the 58 studies, 32 and 26 studies recruited participants from hospital and community settings, respectively. Most studies included general population, whereas 4 studies included specific populations, e.g., white-collar workers(26, 67), male football players(41), and male military workers(38). Twenty-one studies included participants who had not been prior diagnosed with HT, whereas 37 studies included both participant who had or had not been diagnosed with HT.
Risk of bias assessment
Results of risk of bias assessment are presented in Additional Table 1. Almost all CBPM studies (94.44%) were low risk in all domains of applicability. Eight(21, 32, 39, 40, 45, 51, 53, 58) (16.7%) and 7 (12.9%) studies(31, 35, 42, 47, 50, 56, 59) were high and unclear bias in selection of study subjects. Fifty-two studies(10, 12, 20-32, 34-39, 41-67, 71, 72, 74) (96.3%) applied the index/study test before the reference standard, but with unclear explanation of blinding. Thirty-eight studies (70.4%) were high or unclear risk of bias in flows and timing because they did not report the time interval between the study test and the reference standard, or they also excluded subjects with invalid test results or those lost to follow up. All HBPM studies were low risk of bias in all domains of applicability. Six studies (75%) applied the index test before the reference standard without blinding information, and 4 studies (50%) were high risk of bias in their flow and timing.
Pooling CBPM diagnostic performances
Among 54 CBPM studies, 31 studies(7, 10, 12, 20-35, 41, 59-67, 72, 73) reported 2x2 table data which could be assessed for diagnostic performance, while 7(36-40, 42, 43) and 16(44-58, 71) studies reported data for only positive and negative CBPM respectively (see Table 1).
Among the 31 studies with 2x2 data, 29(7, 10, 12, 21-35, 41, 59-64, 67, 73, 74) and 1(20) studies used a cutoff threshold of ≥140/90 and DBP > 95 mmHg for diagnosis of HT. The cut-offs of ABPM were 125-130/79-80 for 24-hr(12, 27, 32-34, 59, 60, 62-64, 74) and 135-140/85-91mmHg for day-time/awake(7, 20-26, 28-31, 35, 61, 66, 67, 73). The mean age ranged from 28 to 62 years and percent male ranged from 35% to 100%(see Table 1).
These 2x2 data (n = 66,767) were used for pooling diagnostic characteristics of CBPM versus ABPM, see Additional Table 2. The pooled sensitivity and specificity were 70% (95% CI: 63%, 76%; I2 = 98.56%) and 81% (95% CI: 73%, 87%; I2 = 99.47%) with high heterogeneity, see Figure 2 a-b. Pooled LR+ and LR- were 3.67 (95% CI: 2.69, 5.00; I2 = 99.35%) and 0.37 (95% CI: 0.31-0.44; I2 = 98.57%), see Additional Figure 1. These diagnostic characteristics all require setting a threshold and trading off sensitivity for specificity or LR+ for LR- , hence they must be judged in pairs. For example, given a pretest probability of HT of 44%, the post-test probability was increased to 74% if CBPM was positive, or reduced to 23% if CBPM was negative (see Fagan’s plot Figure 3a). Alternatively, a single measure of diagnostic performance, i.e., the DOR was 9.84 (95% CI: 6.82, 14.20; I2 = 100%), see Additional Figure 1c. The HSROC reflects diagnostic performance across the entire range of possible threshold values; in this case, the pooled HSROC was 0.81 (95% CI: 0.72, 0.88) indicating moderately good discrimination for judging presence of HT (Additional Figure 2a). Deek’s funnel plot showed no evidence of publication bias (Additional Figure 3a).
Subgroup analysis
Subgroup analyses were performed by types of ABPM, age group (< 50 and ≥50 years), percent males (< 50% and ≥50%), number of repeated measurements of CBPM (1, 2-5 times), setting of studies (community and hospital-based), and type of patients (no HT, mixed HT with non-HT). The degrees of heterogeneity (I2) did not decrease for each sub-group of these factors (Additional Table 3), but performances of CBPM improved in some sub-groups including age group ≤50 year, percent male ≤50%, and community-based setting with the LR+ of 5.1 (95% CI: 3.0, 8.7), 5.8 (95% CI: 3.5, 9.8), and 6.0 (95% CI: 3.9, 9.3), respectively.
Pooling HBPM diagnostic performances
Eight HBPM studies(7, 68-74) reported 2x2 data (Additional Table 4) with cutoff threshold of 135/85(68-72, 74) (N=6) and 140/90(7, 74) (N=2) mmHg and measurement duration about 3 to 7 days, see Table 1. Mean age and percent male ranged from 48.1 to 51.8 years and 46.5% to 54.9% respectively. Among them, 4, 3, and 1 studies applied 24-hr ABPM, day/awake ABPM, and multiple periods, respectively.
The overall pooled sensitivity and specificity were respectively 74% (95% CI: 66%, 80%; I2 = 95.52%) and 83% (95% CI: 76%, 89%; I2 = 90.20%), see Figures 2 c-d. The pooled DOR, LR+ and LR-were 13.73 (95% CI: 8.55, 22.03; I2 = 99.99%), 4.36 (95% CI: 3.04, 6.27; I2 = 75.06%), and 0.32 (95% CI: 0.25, 0.41; I2 = 94.34%), see Additional Figure 4 a-c. Again, given a pretest-probability of 44%, a positive HBPM would result in a post-test probability of 77%, while a negative HBPM would reduce the probability to 20% (Figure 3b). The pooled HSROC was 0.85 (95% CI: 0.82, 0.88), again suggesting moderately good discrimination, see Additional Figure 2b. Sub-group analysis could not be performed due to the small number of included studies. Deek’s funnel plot indicated no evidence of publication bias, see Additional Figure 3b.
Pooling prevalence of WCHT and MHT by CBPM
Seven(36-40, 42, 43) and 16 studies(44-58, 65) reported only data of WCHT and MHT, see Table 1. These studies were then combined with 31 CBPM studies with 2x2 data above, yielding a total of 38 and 47 studies for pooling proportions of WCHT and MHT respectively. Among the 38 studies with WCHT, time of ABPM measures were 24-hr (N=13), day-time/awake (N=23), and multiple periods (N=2). Among the 47 studies with MHT, ABPM measures were 24-hr (N=13), day-time/awake (N=24), and multiple times (N=7), both 24-hr and daytime (N = 4), and daytime and nighttime (N=1).
Data for the 38 (n = 32685) and 47 (n = 47713) studies for WCHT and MHT are provided in Additional Tables 5 and 6. The pooled proportions of WCHT and MHT were 0.28 (95% CI: 0.25, 0.32) and 0.27 (95% CI: 0.22, 0.31) with corresponding I2 of 97.64% and 99.36% respectively, see Figures 4a and 4b. Subgroup analyses were performed, but none of the co-variables could decrease the degree of heterogeneity (see Additional Table 7). However, subgroup of repeated measures of CBPM 4-5 times and 24-hr ABPM could respectively reduce the pooled WCHT from 0.28 to 0.23 (95% CI: 0.16, 0.31) and 0.23 (95% CI: 0.18, 0.28). Likewise, repeated CBPM measure could reduce the pooled MHT from 0.27 to 0.15 (95% CI: 0.10, 0.19) whereas the 24-hr ABPM conversely increased the prevalence to 0.33 (95% CI: 0.22, 0.43).
Pooling prevalence of WCHT and MHT by HBPM
Eight HBPM studies were included for pooling WCHT (n = 1979) and MHT (n = 1939), see Additional Table 4. The pooled prevalence of WCHT and MHT were 0.17 (95% CI: 0.11, 0.22) and 0.30 (95% CI: 0.19, 0.42) with the corresponding I2 of 88.62% and 97.32%, see Figures 4 c-d.