I'm attempting to convert from world space coordinates to screen space coordinates.

I have the following code to transform my object position

Vector3 screenSpacePoint = Vector3.Transform(object.WorldPosition, camera.ViewProjectionMatrix);

The value does not appear to be in screen space coordinates and is not limited to a [-1, 1] range.

What step have I missed out in the conversion process?

EDIT:

Projection Matrix

Perspective(game.GraphicsDevice.Viewport.AspectRatio, nearClipPlaneZ, farClipPlaneZ);

    private void Perspective(float aspect_Ratio, float z_NearClipPlane, float z_FarClipPlane)
    {
        nearClipPlaneZ = z_NearClipPlane;
        farClipPlaneZ = z_FarClipPlane;

        float yZoom = 1f / (float)Math.Tan(fov * 0.5f);
        float xZoom = yZoom / aspect_Ratio;

        matrix_Projection.M11 = xZoom;
        matrix_Projection.M12 = 0f;
        matrix_Projection.M13 = 0f;
        matrix_Projection.M14 = 0f;

        matrix_Projection.M21 = 0f;
        matrix_Projection.M22 = yZoom;
        matrix_Projection.M23 = 0f;
        matrix_Projection.M24 = 0f;

        matrix_Projection.M31 = 0f;
        matrix_Projection.M32 = 0f;
        matrix_Projection.M33 = z_FarClipPlane / (nearClipPlaneZ - farClipPlaneZ);
        matrix_Projection.M34 = -1f;

        matrix_Projection.M41 = 0f;
        matrix_Projection.M42 = 0f;
        matrix_Projection.M43 = (nearClipPlaneZ * farClipPlaneZ) / (nearClipPlaneZ - farClipPlaneZ);
        matrix_Projection.M44 = 0f;
    }

View Matrix

        // Make our view matrix
        Matrix.CreateFromQuaternion(ref orientation, out matrix_View);

        matrix_View.M41 = -Vector3.Dot(Right, position);
        matrix_View.M42 = -Vector3.Dot(Up, position);
        matrix_View.M43 = Vector3.Dot(Forward, position);
        matrix_View.M44 = 1f;

        // Create the combined view-projection matrix
        Matrix.Multiply(ref matrix_View, ref matrix_Projection, out matrix_ViewProj);

        // Update the bounding frustum
        boundingFrustum.SetMatrix(matrix_ViewProj);