\documentclass{article}
\usepackage{threeparttable}
\usepackage{multirow}
\usepackage{booktabs}
\usepackage{xcolor}
\begin{document}
\begin{table}[!ht]
\setlength\tabcolsep{0pt}
\centering
\begin{threeparttable}
\begin{tabular}{@{\extracolsep{2ex}}*{7}{lcccccc}}
\toprule
 &  & \multicolumn{5}{c}{\textbf{group1}} \\
\cmidrule{3-7}
 &  & A & \multicolumn{3}{c}{B} & missing \\
 &  & \textbf{group2} & \multicolumn{3}{c}{\textbf{group2}} & \textbf{group2} \\
\cmidrule{3-3}\cmidrule{4-6}\cmidrule{7-7}
 & \textbf{Total} & D & D & missing & Total & missing \\
\midrule
\textbf{value} &  &  &  &  &  &  \\
\hspace{12.0pt}Mean (SD) & 3.5 (1.87) & 2 (1.41) & 4 (NaN) & 5 (NaN) & 4.5 (0.707) & 4 (2.83) \\
\hspace{12.0pt}Median [Min, Max] & 3.5 [1, 6] & 2 [1, 3] & 4 [4, 4] & 5 [5, 5] & 4.5 [4, 5] & 4 [2, 6] \\
\bottomrule
\end{tabular}
\end{threeparttable}
\end{table}
\end{document}