Goldberg D P, Oldehinkel T, Ormel J
Institute of Psychiatry, London.
Psychol Med. 1998 Jul;28(4):915-21. doi: 10.1017/s0033291798006874.
No convincing explanation has been forthcoming for the variation in best threshold to adopt for the GHQ in different settings.
Data dealing with the GHQ and the CIDI in 15 cities from a recent WHO study was subjected to further analysis.
The mean number of CIDI symptoms for those with single diagnoses, or those with multiple diagnoses, does not vary between cities. However, the best threshold is found to be related to the prevalence both of single and of multiple diagnoses in a centre. Variations in the diagnoses to be included in the 'gold standard' did not account for the variation observed. There was a strong relationship between area under the ROC curve (as a measure of the discriminatory power of the GHQ) and the best threshold, with higher thresholds being associated with superior performance of the GHQ. The items on the GHQ-12 that provided most discrimination between cases and non-cases varied from one centre to another.
The GHQ threshold is partly determined by the prevalence of multiple diagnoses, with higher thresholds being associated by higher rates of both single and multiple diagnosis. The mean GHQ score for the whole population of respondents provides a rough guide to the best threshold. In those centres where the discriminatory power of the GHQ is lowest, it is necessary to use a low threshold as a way of ensuring that sensitivity is protected, but the positive predictive value of the GHQ is then lower. Some of the variation between centres is due to variation in the discriminatory power of different items.
对于在不同环境中采用的GHQ最佳阈值的差异，尚未有令人信服的解释。
对世界卫生组织最近一项研究中15个城市的GHQ和CIDI数据进行了进一步分析。
单一诊断者或多重诊断者的CIDI症状平均数在各城市之间没有差异。然而，发现最佳阈值与一个中心的单一诊断和多重诊断患病率均相关。“金标准”中所包含诊断的差异并不能解释所观察到的差异。ROC曲线下面积（作为GHQ鉴别力的一种衡量指标）与最佳阈值之间存在很强的关系，阈值越高，GHQ的表现越好。GHQ-12中对病例和非病例区分度最高的项目在不同中心之间有所不同。
GHQ阈值部分由多重诊断的患病率决定，阈值越高，单一诊断和多重诊断的发生率越高。所有受访者的平均GHQ分数为最佳阈值提供了一个大致的指导。在GHQ鉴别力最低的那些中心，有必要使用低阈值以确保敏感性，但此时GHQ的阳性预测值较低。不同中心之间的一些差异是由于不同项目鉴别力的差异所致。
