A test device for quantifying one or more vitamin D molecules comprising: (a) a housing, containing therein: (i) a sample application pad configured to absorb a biological sample and transport said biological sample to a conjugate pad; (ii) said conjugate pad comprising a vitamin D binding antibody that specifically binds to one or more vitamin D molecules; and (iii) a detection zone comprising a first region having immobilized thereon a detection antibody that specifically binds an epitope that is generated by complexing said vitamin D binding antibody with said one or more vitamin D molecules, wherein said sample application pad, said conjugate pad, and said detection zone are aligned from upstream to downstream along a fluid path through which said biological sample travels, characterized in that said detection antibody comprises a light chain and a heavy chain, wherein: (i) said light chain comprises an amino acid sequence according to SEQ ID NO: 20, and said heavy chain comprises an amino acid sequence according to SEQ ID NO: 12; (ii) said light chain comprises an amino acid sequence according to SEQ ID NO: 2, and said heavy chain comprises an amino acid sequence according to SEQ ID NO: 13; or (iii) said light chain comprises an amino acid sequence according to SEQ ID NO: 19, and said heavy chain comprises an amino acid sequence according to SEQ ID NO: 9. (a) a housing, containing therein: (i) a sample application pad configured to absorb a biological sample and transport said biological sample to a conjugate pad; (ii) said conjugate pad comprising a vitamin D binding antibody that specifically binds to one or more vitamin D molecules; and (iii) a detection zone comprising a first region having immobilized thereon a detection antibody that specifically binds an epitope that is generated by complexing said vitamin D binding antibody with said one or more vitamin D molecules, wherein said sample application pad, said conjugate pad, and said detection zone are aligned from upstream to downstream along a fluid path through which said biological sample travels, characterized in that said detection antibody comprises a light chain and a heavy chain, wherein: (i) said light chain comprises an amino acid sequence according to SEQ ID NO: 20, and said heavy chain comprises an amino acid sequence according to SEQ ID NO: 12; (ii) said light chain comprises an amino acid sequence according to SEQ ID NO: 2, and said heavy chain comprises an amino acid sequence according to SEQ ID NO: 13; or (iii) said light chain comprises an amino acid sequence according to SEQ ID NO: 19, and said heavy chain comprises an amino acid sequence according to SEQ ID NO: 9. (i) a sample application pad configured to absorb a biological sample and transport said biological sample to a conjugate pad; (ii) said conjugate pad comprising a vitamin D binding antibody that specifically binds to one or more vitamin D molecules; and (iii) a detection zone comprising a first region having immobilized thereon a detection antibody that specifically binds an epitope that is generated by complexing said vitamin D binding antibody with said one or more vitamin D molecules, (i) said light chain comprises an amino acid sequence according to SEQ ID NO: 20, and said heavy chain comprises an amino acid sequence according to SEQ ID NO: 12; (ii) said light chain comprises an amino acid sequence according to SEQ ID NO: 2, and said heavy chain comprises an amino acid sequence according to SEQ ID NO: 13; or (iii) said light chain comprises an amino acid sequence according to SEQ ID NO: 19, and said heavy chain comprises an amino acid sequence according to SEQ ID NO: 9.