The construction and validation of a lead exposure screening tool for pregnant women in Thailand (ThaiL8Is)

Abstract

Objectives: To construct, validate, and implement a new screening tool for lead exposure in Thai pregnant women.

Methods: A cross-sectional study that included three processes: screening tool development, validation, and implementation. The participants were pregnant women who had received antenatal care at district health promotion hospitals. There were 100 pregnant women in Nakhon Si Thammarat province during the validation process, and 30 pregnant women in Phang Nga province during the implementation process. Blood lead levels (BLLs) were analysed by atomic absorption spectrophotometry. The sensitivity and specificity of the screening instrument, as well as the Area Under the Curve (AUC), demonstrate its validity.

Results: There were 80 BLL-related items found through the collection of primary and secondary data and examined for validity and inter-rater reliability by five experts. Six items were excluded because the values were less than the criteria set. Seventy-four items remained with the Item Content Validity Index (I-CVI) = 0.80-1.00, the Content Validity Index Average (S-CVI/Ave) = 0.91, and Kappa scores = 0.76-1.00. After using 74 items collected on pregnant women, only 31 items were included in the validation process. Following that, the pooled eight items with cut-off point scores of 1 had the highest validity, which included systolic blood pressure, diastolic blood pressure, urine sugar, haemoglobin level, occupation, drinking coffee, using chemical products, and education level (ThaiL8Is). The ThaiL8Is in the validation process yielded sensitivity = 80.9%, specificity = 69.8%, and an AUC (95%CI) = 0.78 (0.69-0.87). The implementation process has confirmed the validity of the screening tool; sensitivity = 78.9%, specificity = 81.8%, and the AUC (95%CI) = 0.80 (0.63-0.97).

Conclusions: The ThaiL8Is a valid screening tool for Thai pregnant women. ThaiL8Is' sensitivity in detecting the risk groups for lead exposure can be enhanced by a combination of biochemical markers used in routine prenatal screening. It can be used to screen pregnant women for early indicators of lead exposure prior to a blood lead test.

Keywords: Blood lead levels; Lead exposure; Pregnant women; Screening tool.

Figure 1

The study areas of validation and implementation of the screening tool.

Figure 2

Comparison of ROC curve and AUC between single item and 8 items (8Is), Thailand, 2022 (A) comparison between 8Is, I1-2 and I2-5 (B) comparison between 8Is, I2-6 and I2-8 (C) comparison between 8Is, I2-9 and I3-1-12 (D) comparison between 8Is, I5-10 and I5-18-20.

Figure 3

The results of the implementation of the screening tool (ThaiL8Is), the AUC (95%CI) = 0.80 (0.63–0.97).