The results showed various validity parameters at various cut-off point and several groups and it can be seen that the SRQ has good validity against depression as assessed by the MINI. The optimum cut-off point was different for each group and that the SRQ agreement with MINI depression is good because almost all have values above 0.80. Based on PCA analysis, there are two structural factors on the SRQ, namely the depression and a mixture of somatic and anxiety. The prevalence of depression obtained by 5.9% was slightly different from the NHS 2018 report, which was 6.1% because the sample analyzed only the subjects that answer the questions themselves, while the NHS report still included subjects represented by a companion or caregiver .
The resulting ROC for total subjects, male, female, young, and old shows a similar image with AUC values and they are all above 0.90. This AUC value is even higher than previous studies in China, India, Vietnam, and Afghanistan which only had an AUC of around 0.80, even though it uses different reference instruments such as the Clinical Interview Schedule Revised (CIS-R), Composite International Diagnostic Interview (CIDI), Hopkins Symptom Checklist-25 (HSCL-25) [13-16]. Research using the same questionnaire such as SRQ and MINI was conducted in South Africa with an emergency department setting, the results also showed the AUC value of around 0.80 .
Regarding the forming factors, research in South Africa also showed 2 factors as depression-anxiety and somatic, while research in China showed 3 factors, including depression, anxiety, and somatic. In this study, there were two factors formed, and they include; specifically anxiety-somatic and depression. This shows that there is not much difference with other populations in various countries in terms of the factors forming the SRQ.
Various validity parameters have been provided at various cut-off point and in groups by gender and age by showing the AUC. The agreement between SRQ and MINI depression on this finding is good because the values are above 0.70 and 0.80. These results can be used as a basis for extrapolating, for example, the previous NHS data will be able to calculate the depression rate. A more important need is that the future NHS will also be able to obtain depression rates in the population if they tend not to use the MINI depression mode anymore. Regarding the cut-off point, all groups showed that the optimal cut-off point was between 4 -5 and this is slightly different from previous studies which determined it to be about 5 or even 6 (in women) for any diagnosis .
This validity assessment procedure has been studied and the short and easy questionnaires were shown to be preferable to special ones requiring special skills from the enumerator. These methods have been used in other studies, for example, a patient care questionnaire (PHQ) which was validated with MINI [18, 19]. Besides MINI, the Beck Depression Inventory (BDI) has also been used as a reference by several studies . Moreover, the Center for Epidemiological Study for Depression questionnaire (CES-D) have also been used with certain populations according to the target of the study [21, 22].
SRQ has been used as a CMD screening tool, for example, in Eritrea and Afghanistan [23, 24]. Therefore, this means that both SRQ and Patient Health Questionnaire (PHQ) are good enough but require confirmation for positive screening results from health care facilities . A prevalence of 5.90% and 9.88% was obtained for depression and mental-emotional disorder respectively. However, a survey conducted in Iraq with the use of SRQ-20 as initial screening produced a CMD percentage of 35.5% . In Mexico, SRQ was also used to assess people to be deported for violating the border area and the CMD was found to be 16%. The variation in these results despite the use of the same instrument is associated with the characteristics and conditions of different populations. However, the use of MINI in measuring the prevalence of depression in India was able to produced 2.68% .
The validity assessed is a diagnostic test or a screening tool which is also referred to as convergent and concurrent validity in other studies . Meanwhile, some qualitative research has also been conducted to support the assessment of validity  with the focus on the appropriateness of tools, processes, and data .
The strength of this study was the use of a large sample which is an indication of high representation of the Indonesian population and this means it has the ability to reflect the real situation of the country. However, it was limited for the fact that NHS does not only assessed mental health, but various diseases and matters related to the subject's health. Through all the questions asked in this study, there is the potential for fatigue in both enumerators and respondents.