making difficult things

less difficult

or what we call 'progress'

things that were hard in the past get made easier

which enables the next innovators to tackle the

next hard problem

and make that easier

web

One of the reasons we can do impressive things in the Web is that there are APIs that have wrapped some of the hard stuff in an easy interface

telephony

compute & storage

maps

things that were hard in the past get made easier

which enables the next innovators to tackle the

next hard problem

and make that easier

healthcare IT is hard

no one monolithic system can possibly do everything needed everywhere

so we need to break the monoliths into services

almost nobody disagrees with this

(but unfortunately almost nobody is doing it)

clinical calculator

wraps clinical calculations in a simple API

BMI is easy

bmi = weight_in_kg / ( height_in_m ** 2 )

BMI Centile ain't so easy

  def lms_to_centile(x, lms)
    # formulae taken from http://www.cdc.gov/growthcharts/percentile_data_files.htm
    # x is the measurement under consideration
    # returns the percentile as a number from 0 to 100
    # for more information about generating centile values in code, see this blog post: http://www.bawmedical.co.uk/2014/05/10/centiles-doing-them-in-code-part-1/
    l = lms[:l]
    m = lms[:m]
    s = lms[:s]

    if l == 0
      z = log(x / m) / s
    else
      z = (((x / m)**l) - 1) / (l * s)
    end

    Distribution::Normal.cdf(z) * 100
  end

and then you need this data...

"bmi": {
  "0": { "l": -0.233, "m": 13.281, "s": 0.0926 },
  "1": { "l": -0.398, "m": 14.953, "s": 0.0872 },
  "2": { "l": -0.512, "m": 16.137, "s": 0.0836 },
  "3": { "l": -0.589, "m": 16.844, "s": 0.0813 },
  "4": { "l": -0.641, "m": 17.258, "s": 0.0799 },
  "5": { "l": -0.676, "m": 17.51, "s": 0.079 },
  "6": { "l": -0.698, "m": 17.666, "s": 0.0784 },
  "7": { "l": -0.711, "m": 17.758, "s": 0.078 },
  "8": { "l": -0.718, "m": 17.798, "s": 0.0777 },
  "9": { "l": -0.72, "m": 17.797, "s": 0.0775 },
  "10": { "l": -0.72, "m": 17.763, "s": 0.0774 },
  "11": { "l": -0.718, "m": 17.709, "s": 0.0773 },
  "12": { "l": -0.717, "m": 17.644, "s": 0.0774 },
  "13": { "l": -0.716, "m": 17.572, "s": 0.0774 },
  "14": { "l": -0.716, "m": 17.492, "s": 0.0776 },
  "15": { "l": -0.718, "m": 17.406, "s": 0.0777 },
  "16": { "l": -0.721, "m": 17.316, "s": 0.0779 },
  "17": { "l": -0.726, "m": 17.223, "s": 0.0781 },
  "18": { "l": -0.733, "m": 17.131, "s": 0.0783 },
  "19": { "l": -0.742, "m": 17.04, "s": 0.0785 },
  "20": { "l": -0.753, "m": 16.953, "s": 0.0786 },
  "21": { "l": -0.766, "m": 16.87, "s": 0.0787 },
  "22": { "l": -0.781, "m": 16.793, "s": 0.0788 },
  "23": { "l": -0.797, "m": 16.721, "s": 0.0788 },
  "24": { "l": -0.814, "m": 16.655, "s": 0.0788 },
  "25": { "l": -0.832, "m": 16.595, "s": 0.0788 },
  "26": { "l": -0.851, "m": 16.539, "s": 0.0788 },
  "27": { "l": -0.871, "m": 16.488, "s": 0.0787 },
  "28": { "l": -0.891, "m": 16.441, "s": 0.0787 },
  "29": { "l": -0.912, "m": 16.397, "s": 0.0786 },
  "30": { "l": -0.933, "m": 16.355, "s": 0.0785 },
  "31": { "l": -0.954, "m": 16.315, "s": 0.0784 },
  "32": { "l": -0.975, "m": 16.276, "s": 0.0783 },
  "33": { "l": -0.996, "m": 16.239, "s": 0.0781 },
  "34": { "l": -1.018, "m": 16.203, "s": 0.078 },
  "35": { "l": -1.039, "m": 16.168, "s": 0.0779 },
  "36": { "l": -1.06, "m": 16.133, "s": 0.0777 },
  "37": { "l": -1.08, "m": 16.099, "s": 0.0776 },
  "38": { "l": -1.101, "m": 16.065, "s": 0.0774 },
  "39": { "l": -1.121, "m": 16.031, "s": 0.0773 },
  "40": { "l": -1.141, "m": 15.997, "s": 0.0772 },
  "41": { "l": -1.161, "m": 15.963, "s": 0.0771 },
  "42": { "l": -1.181, "m": 15.93, "s": 0.077 },
  "43": { "l": -1.2, "m": 15.898, "s": 0.0769 },
  "44": { "l": -1.219, "m": 15.867, "s": 0.0769 },
  "45": { "l": -1.237, "m": 15.836, "s": 0.0768 },
  "46": { "l": -1.256, "m": 15.807, "s": 0.0768 },
  "47": { "l": -1.273, "m": 15.779, "s": 0.0768 },
  "48": { "l": -1.291, "m": 15.752, "s": 0.0768 },
  "49": { "l": -1.309, "m": 15.727, "s": 0.0769 },
  "50": { "l": -1.325, "m": 15.704, "s": 0.0769 },
  "51": { "l": -1.342, "m": 15.682, "s": 0.077 },
  "52": { "l": -1.359, "m": 15.662, "s": 0.0771 },
  "53": { "l": -1.375, "m": 15.644, "s": 0.0772 },
  "54": { "l": -1.391, "m": 15.626, "s": 0.0773 },
  "55": { "l": -1.407, "m": 15.61, "s": 0.0775 },
  "56": { "l": -1.422, "m": 15.595, "s": 0.0777 },
  "57": { "l": -1.437, "m": 15.582, "s": 0.0778 },
  "58": { "l": -1.452, "m": 15.569, "s": 0.0781 },
  "59": { "l": -1.467, "m": 15.557, "s": 0.0783 },
  "60": { "l": -1.481, "m": 15.547, "s": 0.0786 },
  "61": { "l": -1.495, "m": 15.538, "s": 0.0788 },
  "62": { "l": -1.509, "m": 15.53, "s": 0.0792 },
  "63": { "l": -1.523, "m": 15.523, "s": 0.0795 },
  "64": { "l": -1.536, "m": 15.517, "s": 0.0798 },
  "65": { "l": -1.549, "m": 15.511, "s": 0.0802 },
  "66": { "l": -1.562, "m": 15.507, "s": 0.0806 },
  "67": { "l": -1.575, "m": 15.503, "s": 0.081 },
  "68": { "l": -1.587, "m": 15.5, "s": 0.0814 },
  "69": { "l": -1.599, "m": 15.498, "s": 0.0819 },
  "70": { "l": -1.611, "m": 15.497, "s": 0.0824 },
  "71": { "l": -1.622, "m": 15.497, "s": 0.0828 },
  "72": { "l": -1.634, "m": 15.498, "s": 0.0833 },
  "73": { "l": -1.644, "m": 15.499, "s": 0.0839 },
  "74": { "l": -1.655, "m": 15.501, "s": 0.0844 },
  "75": { "l": -1.665, "m": 15.503, "s": 0.0849 },
  "76": { "l": -1.675, "m": 15.507, "s": 0.0855 },
  "77": { "l": -1.685, "m": 15.511, "s": 0.0861 },
  "78": { "l": -1.694, "m": 15.516, "s": 0.0866 },
  "79": { "l": -1.704, "m": 15.522, "s": 0.0872 },
  "80": { "l": -1.713, "m": 15.529, "s": 0.0878 },
  "81": { "l": -1.721, "m": 15.536, "s": 0.0884 },
  "82": { "l": -1.73, "m": 15.545, "s": 0.089 },
  "83": { "l": -1.738, "m": 15.554, "s": 0.0896 },
  "84": { "l": -1.745, "m": 15.564, "s": 0.0902 },
  "85": { "l": -1.753, "m": 15.575, "s": 0.0908 },
  "86": { "l": -1.76, "m": 15.587, "s": 0.0915 },
  "87": { "l": -1.767, "m": 15.6, "s": 0.0921 },
  "88": { "l": -1.774, "m": 15.614, "s": 0.0927 },
  "89": { "l": -1.781, "m": 15.628, "s": 0.0933 },
  "90": { "l": -1.787, "m": 15.643, "s": 0.0939 },
  "91": { "l": -1.793, "m": 15.659, "s": 0.0945 },
  "92": { "l": -1.798, "m": 15.675, "s": 0.0951 },
  "93": { "l": -1.804, "m": 15.692, "s": 0.0957 },
  "94": { "l": -1.809, "m": 15.71, "s": 0.0963 },
  "95": { "l": -1.814, "m": 15.729, "s": 0.0969 },
  "96": { "l": -1.818, "m": 15.748, "s": 0.0975 },
  "97": { "l": -1.823, "m": 15.768, "s": 0.0981 },
  "98": { "l": -1.827, "m": 15.789, "s": 0.0986 },
  "99": { "l": -1.83, "m": 15.81, "s": 0.0992 },
  "100": { "l": -1.834, "m": 15.833, "s": 0.0998 },
  "101": { "l": -1.837, "m": 15.855, "s": 0.1003 },
  "102": { "l": -1.84, "m": 15.88, "s": 0.1008 },
  "103": { "l": -1.843, "m": 15.904, "s": 0.1014 },
  "104": { "l": -1.846, "m": 15.929, "s": 0.1019 },
  "105": { "l": -1.848, "m": 15.955, "s": 0.1024 },
  "106": { "l": -1.85, "m": 15.982, "s": 0.1029 },
  "107": { "l": -1.852, "m": 16.009, "s": 0.1034 },
  "108": { "l": -1.854, "m": 16.037, "s": 0.1039 },
  "109": { "l": -1.855, "m": 16.066, "s": 0.1044 },
  "110": { "l": -1.856, "m": 16.095, "s": 0.1048 },
  "111": { "l": -1.857, "m": 16.125, "s": 0.1053 },
  "112": { "l": -1.858, "m": 16.155, "s": 0.1057 },
  "113": { "l": -1.858, "m": 16.187, "s": 0.1062 },
  "114": { "l": -1.859, "m": 16.219, "s": 0.1066 },
  "115": { "l": -1.859, "m": 16.251, "s": 0.107 },
  "116": { "l": -1.859, "m": 16.284, "s": 0.1074 },
  "117": { "l": -1.859, "m": 16.318, "s": 0.1078 },
  "118": { "l": -1.859, "m": 16.352, "s": 0.1082 },
  "119": { "l": -1.858, "m": 16.387, "s": 0.1085 },
  "120": { "l": -1.857, "m": 16.423, "s": 0.1089 },
  "121": { "l": -1.856, "m": 16.459, "s": 0.1092 },
  "122": { "l": -1.855, "m": 16.496, "s": 0.1096 },
  "123": { "l": -1.854, "m": 16.533, "s": 0.1099 },
  "124": { "l": -1.853, "m": 16.57, "s": 0.1102 },
  "125": { "l": -1.851, "m": 16.609, "s": 0.1105 },
  "126": { "l": -1.85, "m": 16.648, "s": 0.1108 },
  "127": { "l": -1.848, "m": 16.687, "s": 0.1111 },
  "128": { "l": -1.846, "m": 16.727, "s": 0.1114 },
  "129": { "l": -1.844, "m": 16.768, "s": 0.1117 },
  "130": { "l": -1.842, "m": 16.808, "s": 0.112 },
  "131": { "l": -1.839, "m": 16.85, "s": 0.1122 },
  "132": { "l": -1.837, "m": 16.892, "s": 0.1125 },
  "133": { "l": -1.834, "m": 16.935, "s": 0.1127 },
  "134": { "l": -1.831, "m": 16.977, "s": 0.113 },
  "135": { "l": -1.829, "m": 17.02, "s": 0.1132 },
  "136": { "l": -1.826, "m": 17.065, "s": 0.1134 },
  "137": { "l": -1.823, "m": 17.108, "s": 0.1136 },
  "138": { "l": -1.819, "m": 17.154, "s": 0.1138 },
  "139": { "l": -1.816, "m": 17.199, "s": 0.114 },
  "140": { "l": -1.813, "m": 17.244, "s": 0.1142 },
  "141": { "l": -1.809, "m": 17.291, "s": 0.1144 },
  "142": { "l": -1.806, "m": 17.338, "s": 0.1146 },
  "143": { "l": -1.802, "m": 17.386, "s": 0.1147 },
  "144": { "l": -1.799, "m": 17.433, "s": 0.1149 },
  "145": { "l": -1.795, "m": 17.481, "s": 0.115 },
  "146": { "l": -1.791, "m": 17.53, "s": 0.1152 },
  "147": { "l": -1.787, "m": 17.579, "s": 0.1153 },
  "148": { "l": -1.783, "m": 17.629, "s": 0.1155 },
  "149": { "l": -1.78, "m": 17.679, "s": 0.1156 },
  "150": { "l": -1.776, "m": 17.729, "s": 0.1157 },
  "151": { "l": -1.771, "m": 17.779, "s": 0.1158 },
  "152": { "l": -1.767, "m": 17.83, "s": 0.1159 },
  "153": { "l": -1.763, "m": 17.881, "s": 0.116 },
  "154": { "l": -1.759, "m": 17.933, "s": 0.1161 },
  "155": { "l": -1.755, "m": 17.985, "s": 0.1162 },
  "156": { "l": -1.75, "m": 18.037, "s": 0.1163 },
  "157": { "l": -1.746, "m": 18.089, "s": 0.1164 },
  "158": { "l": -1.742, "m": 18.142, "s": 0.1165 },
  "159": { "l": -1.738, "m": 18.194, "s": 0.1166 },
  "160": { "l": -1.733, "m": 18.247, "s": 0.1166 },
  "161": { "l": -1.729, "m": 18.3, "s": 0.1167 },
  "162": { "l": -1.724, "m": 18.354, "s": 0.1167 },
  "163": { "l": -1.72, "m": 18.407, "s": 0.1168 },
  "164": { "l": -1.715, "m": 18.46, "s": 0.1169 },
  "165": { "l": -1.711, "m": 18.514, "s": 0.1169 },
  "166": { "l": -1.707, "m": 18.567, "s": 0.117 },
  "167": { "l": -1.702, "m": 18.621, "s": 0.117 },
  "168": { "l": -1.697, "m": 18.675, "s": 0.117 },
  "169": { "l": -1.693, "m": 18.729, "s": 0.1171 },
  "170": { "l": -1.689, "m": 18.783, "s": 0.1171 },
  "171": { "l": -1.684, "m": 18.836, "s": 0.1171 },
  "172": { "l": -1.68, "m": 18.89, "s": 0.1172 },
  "173": { "l": -1.675, "m": 18.944, "s": 0.1172 },
  "174": { "l": -1.671, "m": 18.997, "s": 0.1172 },
  "175": { "l": -1.666, "m": 19.051, "s": 0.1172 },
  "176": { "l": -1.661, "m": 19.104, "s": 0.1172 },
  "177": { "l": -1.657, "m": 19.158, "s": 0.1172 },
  "178": { "l": -1.652, "m": 19.211, "s": 0.1172 },
  "179": { "l": -1.648, "m": 19.264, "s": 0.1172 },
  "180": { "l": -1.643, "m": 19.317, "s": 0.1173 },
  "181": { "l": -1.639, "m": 19.37, "s": 0.1173 },
  "182": { "l": -1.635, "m": 19.423, "s": 0.1173 },
  "183": { "l": -1.63, "m": 19.475, "s": 0.1172 },
  "184": { "l": -1.626, "m": 19.528, "s": 0.1172 },
  "185": { "l": -1.621, "m": 19.579, "s": 0.1172 },
  "186": { "l": -1.617, "m": 19.632, "s": 0.1172 },
  "187": { "l": -1.612, "m": 19.683, "s": 0.1172 },
  "188": { "l": -1.608, "m": 19.735, "s": 0.1172 },
  "189": { "l": -1.603, "m": 19.786, "s": 0.1172 },
  "190": { "l": -1.599, "m": 19.837, "s": 0.1172 },
  "191": { "l": -1.595, "m": 19.887, "s": 0.1171 },
  "192": { "l": -1.59, "m": 19.938, "s": 0.1171 },
  "193": { "l": -1.586, "m": 19.988, "s": 0.1171 },
  "194": { "l": -1.582, "m": 20.038, "s": 0.1171 },
  "195": { "l": -1.577, "m": 20.087, "s": 0.1171 },
  "196": { "l": -1.573, "m": 20.137, "s": 0.117 },
  "197": { "l": -1.569, "m": 20.186, "s": 0.117 },
  "198": { "l": -1.564, "m": 20.234, "s": 0.117 },
  "199": { "l": -1.56, "m": 20.282, "s": 0.117 },
  "200": { "l": -1.556, "m": 20.33, "s": 0.1169 },
  "201": { "l": -1.551, "m": 20.378, "s": 0.1169 },
  "202": { "l": -1.547, "m": 20.425, "s": 0.1169 },
  "203": { "l": -1.543, "m": 20.472, "s": 0.1168 },
  "204": { "l": -1.538, "m": 20.519, "s": 0.1168 },
  "205": { "l": -1.534, "m": 20.565, "s": 0.1168 },
  "206": { "l": -1.53, "m": 20.611, "s": 0.1167 },
  "207": { "l": -1.526, "m": 20.656, "s": 0.1167 },
  "208": { "l": -1.521, "m": 20.702, "s": 0.1167 },
  "209": { "l": -1.517, "m": 20.746, "s": 0.1166 },
  "210": { "l": -1.513, "m": 20.791, "s": 0.1166 },
  "211": { "l": -1.509, "m": 20.836, "s": 0.1166 },
  "212": { "l": -1.505, "m": 20.879, "s": 0.1165 },
  "213": { "l": -1.501, "m": 20.923, "s": 0.1165 },
  "214": { "l": -1.496, "m": 20.967, "s": 0.1165 },
  "215": { "l": -1.492, "m": 21.009, "s": 0.1164 },
  "216": { "l": -1.488, "m": 21.052, "s": 0.1164 },
  "217": { "l": -1.484, "m": 21.095, "s": 0.1164 },
  "218": { "l": -1.48, "m": 21.136, "s": 0.1163 },
  "219": { "l": -1.476, "m": 21.178, "s": 0.1163 },
  "220": { "l": -1.472, "m": 21.22, "s": 0.1162 },
  "221": { "l": -1.467, "m": 21.26, "s": 0.1162 },
  "222": { "l": -1.463, "m": 21.301, "s": 0.1162 },
  "223": { "l": -1.459, "m": 21.342, "s": 0.1161 },
  "224": { "l": -1.455, "m": 21.382, "s": 0.1161 },
  "225": { "l": -1.451, "m": 21.422, "s": 0.1161 },
  "226": { "l": -1.447, "m": 21.461, "s": 0.116 },
  "227": { "l": -1.443, "m": 21.501, "s": 0.116 },
  "228": { "l": -1.439, "m": 21.54, "s": 0.1159 },
  "229": { "l": -1.435, "m": 21.578, "s": 0.1159 },
  "230": { "l": -1.431, "m": 21.617, "s": 0.1159 },
  "231": { "l": -1.427, "m": 21.655, "s": 0.1158 },
  "232": { "l": -1.423, "m": 21.693, "s": 0.1158 },
  "233": { "l": -1.419, "m": 21.73, "s": 0.1158 },
  "234": { "l": -1.415, "m": 21.768, "s": 0.1157 },
  "235": { "l": -1.412, "m": 21.805, "s": 0.1157 },
  "236": { "l": -1.408, "m": 21.842, "s": 0.1157 },
  "237": { "l": -1.404, "m": 21.878, "s": 0.1156 },
  "238": { "l": -1.4, "m": 21.914, "s": 0.1156 },
  "239": { "l": -1.396, "m": 21.951, "s": 0.1155 },
  "240": { "l": -1.392, "m": 21.986, "s": 0.1155 },
  "241": { "l": -1.388, "m": 22.022, "s": 0.1155 },
  "242": { "l": -1.385, "m": 22.058, "s": 0.1154 },
  "243": { "l": -1.381, "m": 22.093, "s": 0.1154 },
  "244": { "l": -1.377, "m": 22.128, "s": 0.1154 },
  "245": { "l": -1.373, "m": 22.162, "s": 0.1153 },
  "246": { "l": -1.369, "m": 22.197, "s": 0.1153 },
  "247": { "l": -1.366, "m": 22.231, "s": 0.1153 },
  "248": { "l": -1.362, "m": 22.266, "s": 0.1152 },
  "249": { "l": -1.358, "m": 22.299, "s": 0.1152 },
  "250": { "l": -1.354, "m": 22.333, "s": 0.1152 },
  "251": { "l": -1.351, "m": 22.367, "s": 0.1151 },
  "252": { "l": -1.347, "m": 22.4, "s": 0.1151 },
  "253": { "l": -1.343, "m": 22.433, "s": 0.1151 },
  "254": { "l": -1.34, "m": 22.467, "s": 0.115 },
  "255": { "l": -1.336, "m": 22.499, "s": 0.115 },
  "256": { "l": -1.332, "m": 22.532, "s": 0.115 },
  "257": { "l": -1.329, "m": 22.565, "s": 0.1149 },
  "258": { "l": -1.325, "m": 22.597, "s": 0.1149 },
  "259": { "l": -1.322, "m": 22.629, "s": 0.1149 },
  "260": { "l": -1.318, "m": 22.662, "s": 0.1148 },
  "261": { "l": -1.314, "m": 22.693, "s": 0.1148 },
  "262": { "l": -1.311, "m": 22.725, "s": 0.1148 },
  "263": { "l": -1.307, "m": 22.757, "s": 0.1147 },
  "264": { "l": -1.304, "m": 22.788, "s": 0.1147 },
  "265": { "l": -1.3, "m": 22.82, "s": 0.1147 },
  "266": { "l": -1.297, "m": 22.851, "s": 0.1146 },
  "267": { "l": -1.293, "m": 22.882, "s": 0.1146 },
  "268": { "l": -1.29, "m": 22.913, "s": 0.1146 },
  "269": { "l": -1.286, "m": 22.945, "s": 0.1146 },
  "270": { "l": -1.283, "m": 22.975, "s": 0.1145 },
  "271": { "l": -1.279, "m": 23.005, "s": 0.1145 },
  "272": { "l": -1.276, "m": 23.036, "s": 0.1145 },
  "273": { "l": -1.272, "m": 23.067, "s": 0.1144 },
  "274": { "l": -1.269, "m": 23.097, "s": 0.1144 },
  "275": { "l": -1.266, "m": 23.127, "s": 0.1144 },
  "276": { "l": -1.263, "m": 23.154, "s": 0.1143 }
}

and then you'd need to know what to do with it all

and clinically assure the answers

and keep up with any changes to the centile reference data

or you could just use

other candidates

questions